Argentine forward Lavezzi's low shot slipped under Helton's body in the 61st minute as PSG leapfrogged Porto into first place with 15 points from six games, two ahead of the 2004 champions.
"We produced a good performance. We needed to regain this footballing quality and this attitude," PSG coach Carlo Ancelotti told a news conference after his side bounced back from losing three of their previous five games in Ligue 1.
"The players showed a lot of pride tonight because the critics have been very harsh. Now we can forget the Champions League for a while and focus on Ligue 1."
Ancelotti's team went ahead in the 29th minute when Thiago Silva nodded in a Maxwell free-kick but Porto levelled four minutes later with a far-post header from Jackson Martinez ending a flowing move.
"I am not satisfied," said Porto coach Vitor Pereira. "We were far more aggressive when PSG visited us," he added, referring to his team's 1-0 victory in October.
"This is what we lacked tonight. We regained it when we went 2-1 behind but unfortunately we did not manage to get an equaliser."
