Adebayor celebrates after scoring his third goal of the season
Emmanuel Adebayor kept up his record of scoring in every league game this season to help Manchester City maintain their 100% start to the season.
The Togo striker rose above the Pompey defence to thump in a header from Gareth Barry's excellent corner.
Micah Richards had a goal ruled out for offside as City turned the screw.
After the break, John Utaka fizzed a shot narrowly wide, while fellow substitute David Nugent hit his volley straight at City goalkeeper Shay Given.
The win pushed City up to fourth in the table with nine points out of nine, three points behind Chelsea and Tottenham Hotspur who lead the table with 12 points from four matches.
With wealthy owners at the helm of each club - Pompey's takeover by Sulaiman Al Fahim going through only on Thursday - it was a fascinating meeting between two sides who represent the new wave of the Premier League.
Hughes praises Man City defence
City, though, are 12 months into their new ownership and further down the road of realising their potential.
As a result, the big name stars they have attracted - and the team's greater cohesion - proved too strong for a much-changed Portsmouth side.
While it will take a while for Pompey to stabilise after a period of uncertainty - and to bed in new players - City are showing signs that their revolution is gaining momentum.
Adebayor was once again in excellent form, providing the fulcrum for his side's attacks, and Joleon Lescott - finally making his league debut for City after a protracted move from Everton - gave an assured performance.
Initially, however, Pompey more than held their own, despite fielding a team with five changes from their last league game.
Tommy Smith and Michael Brown had completed their moves to Fratton Park in time to make their debuts and were immediately drafted into the starting line-up.
And for a time, the hosts were the better side, passing the ball around neatly and went close through a rasping shot from Frederic Piquionne.
Adebayor inspired by team-mates
Yet there was always the feeling that once City settled, they would pose more of a threat.
That possibility became a reality when Barry swung in a corner from the right and Adebayor nodded home powerfully.
City thought they had doubled their lead when Richards converted a low cross from Craig Bellamy, who started ahead of Robinho, but the goal was ruled out for offside.
After the break, the imposing Adebayor continued to cause Pompey problems and one moment of magic saw him drag the ball between two defenders before forcing a fine save from Asmir Begovic.
And Stephen Ireland lashed a shot over the bar as a Portsmouth struggled to keep their opponents out.
All seemed to be going City's way but they suffered a blow when Richards limped off injured and watching England boss Fabio Capello will share City's concern, as he may want to pick the defender for the upcoming World Cup qualifiers against Slovenia and Croatia.
We should have nicked it - Hart
It signalled a change in fortunes for Pompey and they began to create a few chances - a Hayden Mullins shot was deflected wide and Younes Kaboul headed over.
Utaka went agonisingly close with a fierce drive that flew just past the post and Richard Hughes wasted a great chance when he volleyed wide from 12 yards.
Parity really should have been restored soon after but Nugent hit his shot into the ground and an upright Given saved the ball with his shoulder.
In the end, City did just enough, while Pompey will hope results will pick up when their new signings are eligible and the team starts to gel.
Portsmouth manager Paul Hart: "It is tough at the moment. But we played very well today.
"We restricted City to only a few chances and we should have nicked a draw at the death.
"We played with spirit and discipline against terrific players and went about our job in a proper way. If we can keep doing that we can turn things around."
Manchester City boss Mark Hughes: "We are keeping clean sheets and that always gives you a chance of winning games.
"Fratton Park is a hard place to come and get something but we were always in control of the game. We took the lead and we should really have had a second goal, which we deserved.
"Micah Richards' goal was chalked out for offside, wrongly in my opinion.
"But we have come out of the blocks and made a statement and three wins out of three league games is great for us."
90:00+3:09 The game is over, as the referee blows his whistle.
90:00+2:09 The assistant referee signals for offside against Emmanuel Adebayor. Nadir Belhadj restarts play with the free kick.
90:00+1:21 Anthony Vanden Borre takes a shot. Blocked by Craig Bellamy. Free kick awarded for a foul by Emmanuel Adebayor on Aaron Mokoena.
Direct free kick taken by Niko Kranjcar. Nadir Belhadj produces a cross, John Utaka takes a shot. Shay Given makes a comfortable
87:59 Centre by Shaun Wright-Phillips, Younes Kaboul manages to make a clearance.
87:24 David Nugent takes a shot. Shay Given makes a comfortable save.
86:34 Substitution David Nugent is brought on as a substitute for Richard Hughes.
86:03 Effort on goal by Shaun Wright-Phillips from deep inside the penalty area misses to the right of the goal.
85:21 Craig Bellamy delivers the ball, clearance by Aaron Mokoena.
83:33 Younes Kaboul fouled by Nigel De Jong, the ref awards a free kick. Michael Brown restarts play with the free kick.
82:17 A cross is delivered by Carlos Tevez. Craig Bellamy crosses the ball, save by Asmir Begovic.
80:45 Free kick taken by Niko Kranjcar. Effort on goal by Richard Hughes from just inside the penalty area goes over the target.
80:45 Booking Pablo Zabaleta receives a yellow card.
80:39 Unfair challenge on Nwankwo Kanu by Pablo Zabaleta results in a free kick.
78:17 Strike comes in from Craig Bellamy from the free kick. Corner taken by Gareth Barry from the right by-line, clearance made
by Younes Kaboul. Emmanuel Adebayor takes a shot. Asmir Begovic makes a comfortable save.
78:17 Booking Booking for Aaron Mokoena for unsporting behaviour.
78:12 Aaron Mokoena gives away a free kick for an unfair challenge on Emmanuel Adebayor.
77:11 John Utaka produces a left-footed shot from just outside the penalty box that goes wide left of the target.
76:33 The ball is swung over by Nwankwo Kanu, save by Shay Given.
75:43 A cross is delivered by Nadir Belhadj, Shaun Wright-Phillips gets a block in.
75:43 Substitution Stephen Ireland leaves the field to be replaced by Nigel De Jong.
74:06 Effort from just outside the area by Younes Kaboul goes over the bar.
72:22 Corner from right by-line taken by Niko Kranjcar. Centre by John Utaka, Craig Bellamy manages to make a clearance.
72:22 Substitution Nwankwo Kanu is brought on as a substitute for Frederic Piquionne.
72:22 Hayden Mullins takes a shot. Wayne Bridge gets a block in.
71:21 The official flags Frederic Piquionne offside. Shay Given restarts play with the free kick.
67:37 Substitution John Utaka replaces Tommy Smith.
65:57 Inswinging corner taken left-footed by Gareth Barry, clearance made by Aaron Mokoena.
65:10 Tommy Smith produces a cross, Pablo Zabaleta makes a clearance.
62:24 Younes Kaboul has a headed effort from close range and clears the crossbar.
62:03 Handball decision goes against Gareth Barry. Hayden Mullins takes the free kick.
60:55 Aaron Mokoena challenges Emmanuel Adebayor unfairly and gives away a free kick. Pablo Zabaleta takes the free kick.
60:21 The ball is delivered by Tommy Smith, Kolo Toure makes a clearance.
59:40 Substitution (Man City) makes a substitution, with Pablo Zabaleta coming on for Micah Richards.
58:58 Craig Bellamy takes a shot. Comfortable save by Asmir Begovic.
56:15 Foul by Micah Richards on Niko Kranjcar, free kick awarded. Niko Kranjcar restarts play with the free kick.
55:20 Kolo Toure takes a shot. Save made by Asmir Begovic.
53:40 Centre by Micah Richards, Niko Kranjcar gets a block in. Short corner taken by Gareth Barry from the right by-line, Shot from
just outside the box by Stephen Ireland goes over the bar.
52:36 Emmanuel Adebayor takes a shot. Asmir Begovic makes a save. Shot from 35 yards by Kolo Toure went wide of the right-hand post.
50:39 Foul by Richard Hughes on Emmanuel Adebayor, free kick awarded. The free kick is delivered right-footed by Craig Bellamy from
left wing, clearance by Younes Kaboul. Gareth Barry takes the inswinging corner, save made by Asmir Begovic.
49:32 Frederic Piquionne is caught offside. Joleon Lescott takes the indirect free kick.
49:19 A cross is delivered by Carlos Tevez.
48:22 Richard Hughes challenges Gareth Barry unfairly and gives away a free kick. Joleon Lescott restarts play with the free kick.
47:14 Handball decision goes against Michael Brown. Free kick taken by Kolo Toure.
45:55 Michael Brown takes a shot. Blocked by Stephen Ireland.
45:01 The referee starts the second half.
45:00+1:14 It is the end of the first-half.
43:28 Gareth Barry takes a shot. Blocked by Anthony Vanden Borre. Corner taken by Gareth Barry from the right by-line played to
the near post, Hayden Mullins makes a clearance. Gareth Barry takes the inswinging corner, clearance made by Frederic Piquionne.
Corner from the left by-line taken by Craig Bellamy, clearance by Hayden Mullins.
40:19 Michael Brown concedes a free kick for a foul on Carlos Tevez. Wayne Bridge takes the direct free kick.
39:39 Gareth Barry is ruled offside. Asmir Begovic restarts play with the free kick.
38:53 Corner taken by Carlos Tevez from the left by-line played to the near post, clearance by Anthony Vanden Borre.
35:41 Nadir Belhadj crosses the ball.
34:58 Nadir Belhadj sends in a cross, Kolo Toure manages to make a clearance.
32:25 Younes Kaboul gives away a free kick for an unfair challenge on Shaun Wright-Phillips. Shay Given restarts play with the free
31:36 Gareth Barry concedes a free kick for a foul on Richard Hughes. Nadir Belhadj restarts play with the free kick.
31:11 The ball is swung over by Frederic Piquionne, Kolo Toure makes a clearance.
29:59 The assist for the goal came from Gareth Barry.
29:59 GOAL - Emmanuel Adebayor:Portsmouth 0 - 1 Man City Emmanuel Adebayor grabs a headed goal from inside the six-yard box. Portsmouth 0-1 Man City.
29:33 Micah Richards crosses the ball, Aaron Mokoena gets a block in. Inswinging corner taken by Gareth Barry from the right by-line,
28:07 Frederic Piquionne is flagged offside by the assistant referee. Shay Given restarts play with the free kick.
27:32 Gareth Barry concedes a free kick for a foul on Michael Brown. Free kick taken by Younes Kaboul.
25:52 Michael Brown challenges Stephen Ireland unfairly and gives away a free kick. Free kick taken by Gareth Barry.
25:17 Free kick awarded for an unfair challenge on Shaun Wright-Phillips by Niko Kranjcar. Free kick taken by Gareth Barry.
24:53 Frederic Piquionne produces a cross.
24:02 A cross is delivered by Craig Bellamy, clearance made by Younes Kaboul.
22:35 Stephen Ireland delivers the ball, Aaron Mokoena makes a clearance. Inswinging corner taken by Gareth Barry from the right
by-line played to the near post, clearance by Frederic Piquionne.
22:20 A cross is delivered by Nadir Belhadj, clearance by Joleon Lescott.
22:08 The ball is delivered by Tommy Smith, blocked by Kolo Toure.
18:56 Free kick awarded for a foul by Micah Richards on Frederic Piquionne. Niko Kranjcar takes the free kick.
18:35 Carlos Tevez takes a shot. Save made by Asmir Begovic.
15:17 Niko Kranjcar takes the inswinging corner, Emmanuel Adebayor manages to make a clearance. Corner taken by Niko Kranjcar from
the left by-line, save by Shay Given.
14:19 Free kick awarded for a foul by Aaron Mokoena on Emmanuel Adebayor. Gareth Barry takes the free kick.
13:06 Foul by Michael Brown on Gareth Barry, free kick awarded. Joleon Lescott takes the direct free kick.
11:36 Shot on goal comes in from Carlos Tevez from the free kick.
11:36 Booking Richard Hughes is cautioned.
11:31 Richard Hughes gives away a free kick for an unfair challenge on Gareth Barry.
10:43 Shot by Frederic Piquionne from deep inside the penalty area misses to the right of the target.
7:50 Corner taken by Gareth Barry from the right by-line, clearance by Tommy Smith.
7:22 The ball is swung over by Craig Bellamy.
4:27 The ball is swung over by Shaun Wright-Phillips, save by Asmir Begovic.
1:26 Foul by Michael Brown on Stephen Ireland, free kick awarded. Direct free kick taken by Joleon Lescott.
0:29 Niko Kranjcar takes a shot. Gareth Barry gets a block in.
0:00 The referee gets the match started.
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