Lampard struck a penalty with 10 minutes remaining after a another set-piece foul up allowed Frederic Piquionne to equalise Nicola Anelka's 22nd minute opener as Chelsea ran out 2-1 winners at Stamford Bridge.
Michael Ballack and Salomon Kalou had early chances as Chelsea dominated possession.
Frank Lampard was next up to pepper the away side's goal - this time his 18th minute right-footed was on target, but not strong enough to unsettle the goalkeeper Asmir Begovic.
Four minutes later and the home side pierced the resolute rearguard of Pompey.
Anelka had the easiest of chances to tuck home a smart right-footer past Begovic from six yards out after clever byline play by centre-back Alex set him up.
Portsmouth's first effort on goal almost saw them score, when on 34 minutes Fredric Piquionne fired in a low right-footer which Chelsea goalkeeper Petr Cech could only parry. The ball fell to Hermann Hreidarsson, but he failed to convert the loose ball and it was cleared to safety.
Set piece folly by Chelsea on 40 minutes saw ex-Blue Tal Ben Haim have a free, glancing header but the centre-back was unlucky to see the ball go over the bar.
Within five minutes of the restart and the set-piece demons returned to Chelsea as Portsmouth equalised.
From 25 yards out Jamie O'Hara rammed into the Chelsea defence a fine left-footed free kick. The ball took a double ricochet off first Salomon Kalou and then Ricardo Carvalho. It fell invitingly to Piquionne who smashed the ball home high and wide of Cech from six yards out.
Joe Cole replaced ineffectual Deco a minute later. Avram Grant countered by replacing Papa Bouba Diop with Richard Hughes.
Begovic produced a fine save on 66 minutes to prevent substitute Florent Malouda first touch going in, but the home side regained the lead with 12 minutes remaining.
Marc Wilson upended Branislav Ivanovic in the penalty area and Lampard leathered the ball into the net.
Joe Cole was denied when he failed to tuck home from a tight angle three minutes from time, though in truth Portsmouth deserved nothing and that's exactly what they got.