Monaco win 5-3 on aggregate
Chelsea paid the price for missing a string of chances at Stamford Bridge as their hopes of reaching the Champions League final were dashed by Monaco.
Jesper Gronkjaer's looping cross-shot and a Frank Lampard strike put Chelsea ahead in the tie after both sides had hit the woodwork in a frantic opening.
But Hugo Ibarra followed up after a Fernando Morientes header rebounded off the post for a vital Monaco away goal.
And Morientes pounced on the hour to book a meeting with Porto in the final.
Chelsea chose measured build-up over all-out attack as they set about overturning a two-goal deficit from the first leg in Monaco.
But the result was a first half which could have seen them score at least five times, and Monaco three.
The first chance fell to Chelsea's Jimmy-Floyd Hasselbaink after just 35 seconds as he found space in the centre before shooting weakly into the arms of Flavio Roma.
21 mins: Gronkjaer puts Chelsea ahead
24 mins: Morientes hits the post
32 mins: Gudjohnsen heads against the bar
43 mins: Lampard's shot makes it 2-0
45 mins: Ibarra follows up Morientes' header
50 mins: Gronkjaer blazes over from close range
59 mins: Morientes wins the tie for Monaco
Then Joe Cole looked certain to score when Roma could only parry a fierce drive from Geremi, only to slice wide with the goal at his mercy.
It took a superb save from Roma to deny Hasselbaink from close range, but the breakthrough finally came after 21 minutes.
There looked to be little danger when Mario Melchiot fed Gronkjaer on the right, but the Danish winger cut inside and sent a looping shot into the far top corner.
Chelsea had John Terry to thank for deflecting a snapshot from Morientes on to keeper Carlo Cudicini's left-hand post.
Gudjohnsen then headed a pinpoint Hasselbaink cross against the bar from just two yards out, and Lampard had a stinging volley clawed away by Roma.
Morientes looked like he would regret shooting wide from eight yards out when Lampard produced a clinical finish after crisp build-up play from Melchiot and Gudjohnsen to put Chelsea 2-0 up.
But a jubilant Stamford Bridge was hushed into silence on the stroke of half-time when winger Jerome Rothen cut in from the right and Morientes looped a header over Cudicini.
The ball came back off the post and appeared to strike Ibarra on the arm before crossing the line.
Chelsea began the second half as they had done the first - with more gilt-edged chances.
Left-back Wayne Bridge put the ball on a plate for Gudjohnsen after a mazy dribble past two defenders, but the Icelandic striker barely made contact from five yards out.
And then it was Gronkjaer's turn to hang his head as he blazed over the bar after another excellent cross from Bridge.
And Chelsea's hopes of reaching the final in Gelsenkirchen on 26 May faded when Morientes, the architect of Monaco's comeback in the first leg, struck again.
The on-loan Real Madrid striker played a one-two with Lucas Bernardi before coolly driving the ball past Cudicini.
Chelsea: Cudicini, Melchiot (Johnson 64), Gallas, Terry, Bridge, Gronkjaer, Lampard, Geremi (Parker 69), Cole,
Hasselbaink (Crespo 69), Gudjohnsen.
Subs not used: Ambrosio, Babayaro, Stanic, Huth.
Booked: Cole, Johnson.
Monaco: Roma, Evra, Squillaci (Plasil 45), Rodriguez, Givet,
Ibarra, Cisse, Rothen, Bernardi, Morientes (Nonda 81),
Giuly (Prso 67).
Subs not used: Sylva, Oshadogan, Adebayor, El Fakiri.
Booked: Evra, Bernardi, Rothen.
Referee: Anders Frisk (Sweden).