Lavezzi was also on form as he ran rings round the Blucerchiati defence...
Marek Hamsik grabbed the other for the Partenopei who dominated almost the entire match.
The opening ten minutes of the match were very much end to end with Sampdoria having plenty of possession but unable to make any clear cut chances. But Napoli, when they did venture forward looked far more dangerous with Juan Zuniga and Hamsik combining well down the right side.
Sampdoria did have an early chance when Federico Macheda was played in behind Fabiano Santacroce but he took one touch too many, which allowed Paolo Cannavaro to get back and block the youngster's shot.
However on 16 minutes the home side took the lead thanks to a sweeping counter attack. Ezequiel Lavezzi played the ball in to Cavani, who turned Pietro Accardi before slotting home.
Clearly buoyed by the goal, the Partenopei took control of the match with Lavezzi causing a number of problems and he almost created the second soon after, when he pounced on a misunderstanding between Accardi and Gianluca Curci but his cut back across an open goal could only find Reto Ziegler.
Then just before half time Cavani got his second of the game, after Accardi fouled the Uruguayan in the box leaving the referee no choice but to award the spot kick, which Cavani converted, to give his side a two goal lead going into the break.
After the interval, Napoli went on the offensive straight away and got their reward when Lavezzi once more beat Luciano Zauri, before cutting the ball back to Hamsik who calmly slotted into the far corner.
Ten minutes later it was four, as Walter Gargano played Hamsik in behind the Sampdoria defence only for the Slovakian to square the ball to Cavani for his hat-trick.
The away side did have more of the ball in the final half hour but created little and were lucky not to have gone five behind as Curci made a fantastic double save, first from a long range Gargano strike, then from Cristiano Lucarelli's follow up.
Walter Mazzarri's saw out the match and as a result move back into second place in Serie A, four points behind Milan, while Sampdoria slip one place to 12th.