Ronaldo joined Real from Manchester United for around 90 million euros in 2009 and took his goal-scoring exploits to new heights under Mourinho, who left Real Madrid to rejoin Chelsea as manager earlier this week.
Asked in an interview with Spanish television show Punto Pelota why his relationship with Ronaldo had broken down towards the end of last season, Mourinho said the player had not taken criticism well.
"I had only one problem with him, very simple, very basic, which was when a coach criticises a player from a tactical viewpoint trying to improve what in my view could have been improved," he added.
"And at that moment he didn't take it very well because maybe he thinks he knows everything and the coach cannot help him to develop more.
"Cristiano has had three fantastic seasons with me, I don't know if they were the best of his career because he had some fantastic moments with Manchester United.
"I think we created a fantastic situation for him tactically in which he could express all his potential and turn that into records and goals."
Real's failure to win major silverware last season and reports of division in the dressing room have prompted speculation Ronaldo, whose contract runs until June 2015, may be seeking a move away from the Spanish capital.
Club president Florentino Perez has said the 28-year-old would stay and help Real win the 10th European crown they have been chasing since their last continental success in 2002.
"Cristiano Ronaldo is priceless," Perez, who was returned unopposed for another four-year term this week, told an Internet chat organised by El Mundo newspaper on Tuesday.
"We will do it [win the 10th European title]," he added. "And Cristiano will score a goal in the final."
