Kirsten Dunst: Garrett Hedlund is Amazing

ET caught up with On the Road's star-studded cast at Thursday night's premiere in New York City, where Kirsten Dunst was a little shy while talking about her boyfriend Garrett Hedlund, who she met while shooting the film based on the beloved Jack Kerouac classic.

"He's amazing in the film," she smiles. "Yeah, of course he's talented. He's very good in this film. It's a very coveted [role], and [they're] difficult shoes to fill," she says about him playing the role of Dean Moriarty, who's based on real-life beat writer Neal Cassady.

Related: Kristen Stewart's Raciest Outfit Yet at 'On The Road' Premiere

Garrett was similarly full of praise for Kirsten.

"She's fantastic," he gushes. "And in a way, with this role, such a spitting image of who this gal was," he says about her portrayal of Camille, Dean Moriarty's wife. "And Sam [Sam Riley, who plays Sal Paradise] --he's so great. He's going to be a brother for a lifetime."

As for bringing the book's memorably racy scenes to life, Garrett says that there was no way to prepare for them.

"They're just, you know -- they're awkward. It's funny how like, Sam and I were talking and we were much more nervous -- it didn't matter if it were with a gal or a guy -- we were much more nervous for some of the scenes that were just us, you know, talking and fulfilling some of these scenes that really jumped at us from the pages of the book."

Related: Kirsten Dunst Obtains Restraining Order

Kristen Stewart, who stole the show at the premiere in a super-sheer Erdem dress, showed a similar passion for the Walter Salles-directed film.

"I would've done anything for this movie so I'm just more excited to finally have everyone see it after so long," she tells ET.

Check out the video to hear what it was like for Sam Riley to work with his idols Viggo Mortensen and Steve Buscemi.

On the Road hits theaters December 21, 2012.