didier drogba's goal in first-half added time separated the sides as alexis sánchez and pedro rodríguez hit the woodwork for the holders.
chelsea fc will defend a 1-0 lead at the camp nou next week after didier drogba continued his scoring run against fc barcelona with the decisive goal in a tense semi-final first leg.
the london side's run of success against the uefa champions league holders – they have now not lost in the last six fixtures – encouraged their belief that they can reach the final for only the second time. barça were left to reflect on a number of missed opportunities, alexis sánchez and substitute pedro rodríguez striking the woodwork.
barcelona kicked off and immediately signposted what kind of night it could be for chelsea by keeping hold of the ball for 76 seconds. even then the first touch by a blue shirt was halted by an infringement.
a long clearance by petr Čech raised the home team's hopes, drogba catching carles puyol off guard but overrunning the ball. barça's first real threat arrived in the ninth minute, sánchez timing his run perfectly to collect a through pass from andrés iniesta. the forward lifted the ball over the goalkeeper but was denied by the crossbar.
chelsea replied with a gary cahill long throw that caused confusion but the ball would not drop for john terry. the visitors preferred the more scenic route to goal, lionel messi's run winning him valuable space. iniesta's shot was parried by Čech but cesc fàbregas sliced his follow-up and chelsea breathed again.
messi was appearing in fits and starts but every intervention set off alarms in the home defence. from sánchez's cross he stretched Čech with a header. close to half-time his prodded pass released fàbregas but although a dinked effort beat the goalkeeper, ashley cole was there to clear.
chelsea would have been happy to reach the break on level terms but it got better than that. frank lampard switched play magnificently to send ramires haring away down the left. he spied drogba free inside the area and the pass was dispatched first time past víctor valdés for the ivorian's third goal in five games against these opponents.
the goal clearly stung the reigning champions and they began the second half by extending Čech once more, the goalkeeper diving to his left to keep adriano off the scoresheet.
messi was now more involved and twice cahill made timely interceptions. chelsea had another let-off in the 57th minute when messi scooped a delicate pass to sánchez behind the defence, but the ball got stuck under the chilean's feet and the shot went wide.
chelsea were unable to relieve the pressure for long. the visitors won several free-kicks in dangerous positions outside the penalty area but none came to anything as the wall held firm.
with three minutes left Čech came to the rescue again. messi's free-kick was floated this time and nodded on by puyol but the goalkeeper was equal to it. the chelsea no1 was beaten by pedro's low shot deep into added time but the left-hand post came to his rescue and, when sergio busquets sent the rebound high over the bar, chelsea's slender advantage was secure.