Kids in the US can see the trailer before Scooby-Doo.

And they've told CBBC Newsround Online that Daniel Radcliffe, Rupert Grint and Emma Watson look older and have matured into even better actors.

Several fans have noticed that Daniel and Rupert's voices have broken, so they sound older and deeper.

Emily, 14, from Miami, said: "Rupert's voice is really low!"

And Lizzie, 13, from Scottsdale, added: "The kids are much older looking, and their acting has gotten much better. Emma is more natural as Hermione, and Rupert has a bigger part."

The first trailer shows lots of cool clips. US fans told us they've seen the bit where Malfoy hits Harry with a spell, the flying car and lots of Dobby.

House elf Dobby has caused a bit of a stir. Loads of you - including British fans who can see the teaser trailer - reckon he doesn't look how you imagined.