Leonardo – who has also coached Inter and Milan – revealed that the Real Madrid star was previously top of the Ligue 1 outfit's list of targets.
PSG were also unsuccessful in a bid to sign Juventus midfielder Paul Pogba, but Leonardo still feels the club retain one of the best squads in the world.
"Pogba is at the level to play for PSG, of course," Leonardo told Telefoot.
"We thought of him and thought he would be a great investment because he is one of the best midfielders in the world.
"We also thought of signing Ronaldo. I did everything within the written laws to try to get him to Paris but it was impossible to make him leave Real Madrid.
"There is no other team that has the squad of the Paris Saint-Germain (though). No other team has such offensive force.
"The squad has Salvatore Sirigu, Thiago Silva, Thiago Motta, Zlatan Ibrahimovic and then came Edinson Cavani. We wanted this strong central spine. The team is ready for now and for the future."
Leonardo has also praised the efforts of PSG head coach Laurent Blanc, who he feels is vitally important to the ongoing success of the club.
Blanc took over from Carlo Ancelotti in June and has enjoyed early success, leading the club to the top of Ligue 1 and a place in the last 16 of the UEFA Champions League.
"Laurent Blanc is doing some very smart work - he brings a French perspective, which is important," Leonardo added.
"He was a great player, a world champion, someone who experienced a lot of things in Italy and in Spain. He has a global vision and that is important in football today."
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