The pair worked together for three years at Real Madrid before Mourinho departed for Stamford Bridge in the summer.
Despite reported differences between the two men, Mourinho remains full of praise for his fellow Portuguese.
"Coaching him was the highlight of my career," the 50-year-old told France Football. "He's the most professional player I've ever met.
"A coach and player may have their differences at a given time, but it ends there. I don't have any problem.
"Being at a club with Cristiano Ronaldo is the best thing to have happened to me. Why? Because if I let him pass ahead of me he would be mobbed immediately, and I would be free to pass by in no hurry."
Ronaldo has scored 24 goals in 17 games in all competitions this season.