Chelsea have one foot in the Champions League semi-final after Salomon Kalou scored the only goal of the night in the Stadium of Light against Benfica.
The Ivory Coast hit man volleyed home with consummate ease from six yards on 75 minutes from a quick break fashioned by Fernando Torres.
The Blues showed uncharacteristic levels of concentration, something missing from earlier away ties this season to see out the final minutes to give the Londoners their best result of their European campaign this season.
The 1,500 Chelsea fans in Lisbon were treated to a mature performance which showed high levels of energy, tactical nous coupled with grit and determination.
Chelsea also had two Portuguese players in their starting eleven, Paulo Ferreira and Raul Meireles, whereas Benfica had none.
On four minutes the home side had the first chance when a deep free-kick found the head of Aimar, which thankfully was not touched by Ferreira who tried an air-shot clearance on the six-yard box.
The ball fell to safety when it easily could have gone in for an own-goal.
Fernando Torres showed a nice turn of pace on seven minutes byline and sent in a clipped cross.
Unfortunately no Chelsea player had managed to get into a far enough forward position to take advantage.
Ex-Benfica defender Luiz decided to assist the attack on 11 minutes when he raced through the midfield and let fly a speculative but positive shot. The ball went wide of Artur’s goal but signalled Chelsea’s intent of getting an away goal.
The Blues got their first corner of the match on 16 minutes when a fine run by Ramires went to Torres but his shot was deflected out of play. From the resultant kick by Mata, goalkeeper Artur flapped at the ball and was lucky to see it cleared.
Raul Meireles was shown the yellow card for a foul on Gaitán on 19 minutes, and a minute later Cardoso should have scored when the striker got away from John Terry. But his trusty left foot let him down and he screwed the ball wide of Cech’s right post from eight yards out.
A clever chest down, turn and shot by Torres on 23 minutes on the edge of the Benfica penalty area saw the ball sail high over Artur’s crossbar.
Benfica’s midfielder Bruno César was handed a yellow on 26 minutes for upending Meireles.
Cardozo was again in action on 29 minutes but a deep left sided cross was met by the striker, but his header could not be directed on target and it too went over the crossbar.
The home side produced a period of possession which required Luiz and Ferreira to be alert to deny good goal-scoring opportunities developing.
With eight minutes from the half-time whistle, good approach play by Benfica saw César try his arm with a 20-yarder, but his left-footed effort was miserably wide of target.
Torres had an excellent chance a minute later after Ramires set up the Spain forward.
Torres let fly with a left-footer from just inside the penalty area but he hit the effort over the bar.
Meireles took note of Torres effort and tried one himself. Meireles hit a first-time right-footer from 25 yards but Artur produced a fine diving save to his right to parry the ball for a corner.
Neither side made a change at half-time.
Chelsea escaped an early scare when Luiz got his body in the way of a Cardozo pile-driver from close range as the home side sought to get a breakthrough.
Benfica have scored 65 games in a row at home but it was Salomon Kalou who should have scored with a free header from a Torres cross from the right after 50 minutes.
This was reciprocated by Cardozo who forced Cech into smothering his left footer five minutes later.
Juan Mata, who was quiet for the opening exchanges of the second half smacked the Benfica upright on 60 minutes. He beat the offside trap from a kick out by Cech. The Spain midfielder then rounded Artur but took the ball slightly too wide and hit the post with the goal gaping.
Cech was all at sea when a shot by Witsel was deflected off the body of Terry, and looped over Cech but thankfully for the keeper over his bar too.
Cech was quickly in action again on 66 minutes when Gaitán sent in a great ball on the left and it fell invitingly to Jardel. The header was on target but Cech was equal to it and parried the ball to safety.
Meireles's game was over on 67 minutes as he was replaced by Frank Lampard.
Terry produced a trademark last-ditch interception to thwart Cardozo on 71 minutes as Benfica started to turn the screw on the Londoners.
But it was Chelsea who took the lead with just 15 minutes remaining.
Torres, wide on the right, picked up a ball from Ramires. He raced past Jardel, zipped into the area and clipped the ball onto the six-yard box where Kalou raced in and volleyed home with his left foot.
Ferreira, who had not played a competitive game for three months succumbed to cramp on 80 minutes and was replaced by his fellow countryman Jose Bosingwa.
Daniel Sturridge entered the fray two minutes later replacing goal scorer Kalou.
Sub Nolito, only in a minute produced a fine curling right-footer from just inside the Chelsea area.
But the ball was too high and flashed over Cech’s crossbar.
Chelsea could have finished the tie with five minutes on the clock, when a quick break found Sturridge free on the right. Instead of finishing himself, the striker passed to Mata on the left of the area. But the midfielder chipped the ball over Artur’s crossbar.
Benfica could have saved themselves deep into added time when a byline cross was hacked away by Cole who, in truth knew little about where the ball was going. In fact it inched past Cech's goal.
That was the last action and the Blues are clear favourites to progress to the semi-final in eight days time at the Bridge.
Teams: Chelsea: Petr Cech, Paulo Ferreira, David Luiz, John Terry (c), Ashley Cole, John Mikel Obi, Raul Meireles, Salomon Kalou, Juan Mata, Ramires, Fernando Torres
Subs: Ross Turnbull, Jose Bosingwa, Gary Cahill, Michael Essien, Frank Lampard, Daniel Sturridge, Didier Drogba.
Benfica: -2 formations: Artur; Pereira, Luisão (c), Jardel, Emerson; Garcia; Bruno César, Witsel, Gaitán; Aimar, Cardozo.
Subs: Eduardo, Nolito, Matić, Oliveira, Miguel Vitor, Saviola, Rodrigo.
The referee is Paolo Tagliavento from Italy