Bradley Cooper has admitted that he used to be jealous of Leonardo DiCaprio.

Speaking to Shortlist magazine, The Hangover actor said: ''I worked as a doorman all through grad school. I remember taking Leonardo DiCaprio up to his room, and I was in the elevator with him and, like, seven of his friends. It was around the time of Titanic.

''And I remember this guy who looked like a kid, even though we were about the same age, he looked like a little boy. I remember thinking how I was three feet away from this guy, and we were worlds apart.''

Despite achieving worldwide success, the Silver Linings Playbook actor explained that he is still in awe of his co-star Robert De Niro.

Cooper added: ''To this day, I can't believe [I'm friends with him]. He's infectious. You know when you're with some of your friends and you just start to act like them?

''That's what he's like. When you're with him, you find yourself just starting to adopt some of those mannerisms through osmosis. I draw the line at going to get a Mohawk, though.''