Ronaldo and Alberto Gilardino scored first-half goals and AC Milan beat Empoli 3-1 in the Serie A on Saturday to keep alive its hopes of a berth in next season's European Champions League.
Ronaldo's goal in the 12th minute and Gilardino's in 44th gave Milan a 2-1 half-time lead. Giuseppe Favalli added an insurance goal in the 78th.
The victory moved Milan into fifth place in Serie A with 47 points.
"It was hard," Milan midfielder Gennaro Gattuso said. "Fourth place is very important for us. We haven't made calculations. The Champions League is fundamental for the club and for us."
The top two teams earn guaranteed berths in the Champions League, while the next two receive berths in the qualifying phase. Milan climbed within one point of fourth-place Palermo, who lost 3-1 at home to Cagliari.
Earlier on Saturday, AS Roma beat Catania 2-0 to close the gap on Serie A leader Inter Milan.
Inter were held to a 0-0 draw at Reggina -- only the second team after Udinese to stop the defending champions scoring this season.
Inter lead Italy's top division with 80 points, 18 more than Roma. Lazio are third with 55 points after beating 10-man Messina 1-0 for their eighth straight victory.
Also on Saturday, it was: Atalanta 1, Chievo Verona 0; Fiorentina 4, Ascoli 0; Parma 1, Livorno 0; Sampdoria 1, Torino 0; and Siena 2, Udinese 2.
At San Siro, Ronaldo gave Milan the lead, befuddling Empoli's defense with some trademark stepovers and shooting into the roof of the net for his fourth goal in seven games. He also had a second goal disallowed in the 25th for offside.
Luca Saudati equalized with a scissors kick from the edge of the area in the 43rd, but Gilardino restored the lead a minute later by controlling a ball from Ronaldo with his head and volleying into the bottom left corner.
Favalli scored for the Rossoneri from a pass by Andrea Pirlo.