The prolific attacker made the headlines earlier this season by admitting that he was unhappy with life at the club, and a number of recent reports have suggested that he has no intention to sign a new contract with los Blancos.
"Cristiano Ronaldo? Paris Saint-Germain have become a club where anything is possible," Leonardo was quoted as saying by L'Equipe.
He added, "However, he still has an ongoing contract with Real Madrid and we have to realize that he will not leave Madrid for just any club.
"When we are discussing a possible transfer for a player like Cristiano Ronaldo, there are only four or five clubs that can be taken into consideration. Paris Saint-Germain are one of those clubs ..."
However, Leonardo was quick to rule out a move for Barcelona star Lionel Messi as well as Premier League left-back Patrice Evra and Ashley Cole.
"[Messi] will never leave Barcelona," he stated. "With [Christophe] Jallet, Maxwell, [Gregory] van der Wiel and [Sylvain] Armand, I think we have what it takes.
"In the future, we will talk about it, but not now. Cole or Evra? No."
PSG reached the last 16 of Champions League with ease, but the former AC Milan coach went on to say that his current side is not favorites to claim the European title.
"It's certain that Barca are the favorites," he continued. "But we can also say that there are seven games until the final ..."
Zlatan Ibrahimovic has made a considerable impact since joining the club from Milan in the summer, and Leonardo says his form shows that the player is happy at the club.
"Ibra is not only a great man, he has everything. If Ibra and Thiago [Silva] were not happy here, they would not be playing this way."