Then the curtains went down, and the lights dimmed and everyone started to applaud.
A man from Warner Bros came out on the stage and introduced the director first, then the producers, and then the cast members.
When Daniel Radcliffe came on the stage he got the biggest applause of them all.
The director, Alfonso Cuaron told the audience how much he enjoyed working with the cast and making the film.
Whistling and cheering
Then the film started, and when the title appeared on the screen, the entire crowd started applauding, whistling, and cheering.
For a whole year I was waiting for this movie to come out, and I couldn't believe that I was at the premiere seeing this movie with my most favourite actors."
Brooke, 13, Philadelphia, USA
Why don't you write us a Press Pack report - and get it published on the site?!
It can be about anything that's happened in your local area - or your views on the news.