The 27-year-old has been sensational since leaving Manchester United for Real Madrid in a world record £80m deal in 2009, scoring 174 goals in 172 games for the club to date.
But he suggested last year that he was unhappy, and has been linked with a move away from Spain since.
Asked by French journalists whether he would consider joining big-spending Paris Saint-Germain, Ronaldo said: “Yes, everything is possible in life."
However the Portuguese added: “To speak about other clubs would not be good of me while I still have a two-year contract with Real Madrid. Everything is possible in the world of football – but for moment I am okay."