Miley Cyrus stopped Justin Bieber at the premiere of his 3D movie to give him a stern lecture about life in the spotlight.

The former Hannah Montana star attended the unveiling of Bieber's documentary Never Say Never in Los Angeles in 2011 when she grabbed the singer to pass on a word of advice in front of all his fans.

She tells Britain's Elle magazine, "I noticed he was taking all these photos of people and doing a lot of s**t, and I just grabbed him and said, 'Just take a snapshot in your brain of this moment so you don't forget.'"

Cyrus admits she was speaking from experience as she has forgotten the events of her big night in 2009 when she debuted Hannah Montana: The Movie.

She adds, ''I don't remember my Hannah Montana movie premiere and my 3D movie trumped everyone's at the box office. I don't remember being there. All I remember from that night is that I stopped and got a strawberry milkshake beforehand. That's all. It's crazy. You think you're in the present but you're not.''