Kenny Miller's firmly-struck penalty was enough to give Celtic a narrow, if unconvincing, victory over Copenhagen in Champions League Group F.
Kenny Miller (right) scored from the penalty spot
Michael Gravgaard tripped Shunsuke Nakamura in the box and Miller fired the penalty kick past former Rangers goalkeeper Jesper Christiansen.
Christiansen superbly denied Miller a second moments later at Celtic Park.
Copenhagen improved after the break. But, despite some nervous moments, Celtic held on for a deserved win.
The Scottish champions had suffered a pre-match blow when Netherlands striker Jan Vennegoor of Hesselink was ruled out with an ankle injury.
Maciej Zurawski's inclusion up front was the only change from the side that defeated Rangers on Saturday.
The confidence instilled by that victory showed as Celtic dominated possession.
And, when Nakamura exquisitely pulled the ball down 15 yards from goal, Gravgaard had to intervene with a last-ditch block as the Japanese midfielder unleashed his shot.
An Aiden McGeady cross was flicked just wide by the head of Miller and Zurawski had the ball in the net before being ruled offside.
However, Celtic finally made the breakthrough when Gravgaard mistimed another desperate challenge on Nakamura, who took full advantage by collapsing to the deck.
Jesper Christiansen was beaten by Miller's spot kick
It was an obvious penalty nevertheless and Miller made no mistake from the spot, although Christiansen came desperately close to getting a full hand on the ball before it flashed into the corner of the net.
The goalkeeper won the duel moments later, however, making a superb, one-handed stop from Miller's glancing header from eight yards following a Lee Naylor cross.
Copenhagen had started without Jesper Gronkjaer, who suffered a groin injury in their last Champions League game against Benfica.
And, with their attacking options reduced by the loss of the former Chelsea winger, the Danes rarely threatened in the first-half.
But they came out with more purpose after the break and Michael Silberbauer sent a header a few feet over from 10 yards as Celtic suddenly looked under a bit of pressure.
Celtic goalkeeper Artur Boruc was tested for the first time after 65 minutes, holding Hjalte Bo Norregaard's low, 20-yard drive at the second attempt.
Christiansen's legs denied Miller at the other end after McGeady sent the striker clear in the box.
That was the only time the Copenhagen goalkeeper was seriously threatened during a disjointed second 45 minutes.
But a 22-yard drive that Atiba Hutchinson curled a few yards wide after Neil Lennon lost possession was the closest the Danes came to snatching a point.
Celtic: Boruc, Telfer, Caldwell, McManus, Naylor, Nakamura, Lennon, Gravesen, McGeady (Pearson 87), Zurawski (Beattie 73), Miller (Maloney 82).
Subs Not Used: Marshall, Balde, Sno, Jarosik.
Goal: Miller 36 pen.
Copenhagen: Christiansen, Jacobsen, Hangeland, Gravgaard, Bergdolmo (Thomassen 75), Silberbauer, Linderoth, Norregaard, Hutchinson, Berglund (Kvist 55), Allback.
Subs Not Used: Gall, Wendt, Pimpong, Bergvold.
Ref: Florian Meyer (Germany)