Donadoni, the former AC Milan winger who is regarded as one of the greatest Italian players of all time, says he can't compare players from different eras.
"I don't like making comparisons between [Diego] Maradona and [Lionel] Messi, or when they used to make comparisons between Diego or Pele," Donadoni said in an interview with Ole.
"The eras are different. I like Maradona and I like Messi. I like Messi a lot.
"Now, when they speak about Messi and Cristiano Ronaldo," Donadoni went on, "in terms of characteristics, I like Messi more than Ronaldo because he is a different player technically.
"When I watch a match, Messi impresses me more. Ronaldo scores a lot of goals, of course, but I believe that Messi makes the difference more on the pitch.