Napoli could have had three as they also had a goal ruled out for offside.
With the double suspension of Philippe Mexes and Nicolas Burdisso, Claudio Ranieri decided on fielding Marco Cassetti as a makeshift centerback. Something the Napoli tridente of Marek Hamsik, Cavani and Ezequiel Lavezzi certainly looked to exploit.
The game started at pace with both teams having early chances. Roma were looking to Mirko Vucinic for inspiration as the Montenegrin played an wonderful give and go with Fabio Simplicio before unleashing a low shot at Morgan De Sanctis, but the goalkeeper made an excellent stop, clinging on to the ball in the process.
Midway through the first half, Cassetti accused Lavezzi of spitting on him and handbags ensued with both players receiving a yellow card for their troubles.
After an impressive opening, Roma were put under an extended period of pressure from the away side, who had chances from Cavani, Dossena and Hamsik, but each failed to hit the target with their respective efforts.
Though as the first half drew to a close both teams were having a number of issues in retaining ball possession.
However, after the break the game took a turn in Napoli's favor as Juan clipped the heels of Hamsik as he charged into the box and the referee awarded the Partenopei a penalty. Cavani then stepped up and put his team one up.
Though there were protestations from the home side as it seemed the penalty hit both posts, before Cavani then touched the ball again to make sure of the goal.
It was almost a quick fire double as Cavani had another effort punched away by Julio Sergio. Cassetti then had the ball was in the back of his own net but it was ruled out for offside, as Lavezzi crossed from an offside position.
Lavezzi then had a chance to put the game beyond doubt, but one-on-one with Julio Sergio, it was the goalkeeper who came out on top with a well-timed tackle to deny the forward.
Ten minutes from the end, it was ultimately over when Cavani grabbed his second, tapping in from close range following a magnificent Paolo Cannavaro cross from the left wing.
As a result Napoli stay second, three points behind Milan, who also won this evening, while Roma stay in seventh, though they could fall further down the table once the full card of fixtures has been played.