Olivia Wilde thinks Mischa Barton has "one of the most beautiful faces" she's ever seen.

The 39-year-old actress starred alongside Mischa, 37, in the hit teen drama 'The O.C.', and Olivia has recalled being wowed by her co-star the moment they met.

Taking to social media to celebrate the show's 20th anniversary, Olivia - who played Alex Kelly, the on-screen love interest of Mischa's character - wrote on Instagram: "Mischa = one of the most beautiful faces I’ve ever seen. I remember just being like WHOOOAAAA. (sic)"

Olivia previously joked that she would've refused to join the cast "unless [she] got to make out with Mischa".

During an appearance on 'The Howard Stern Show', Olivia also admitted that their love scenes were "so sweet".

Despite this, Olivia has confessed to having mixed feelings about her time on the show.

The actress explained that she was initially embarrassed about her role - but she now feels "lucky" to have been part of the cast.

She told the New York Times newspaper: "I used to dismiss 'The O.C.' ... I did a teen soap - what an embarrassment.' And now I think, ah, that was really formative and I'm lucky I got to do that."

What's more, Olivia admitted to being shocked by the level of interest in the show.

Speaking to the 'Keep It' podcast, the actress explained: "I was just like, 19, just working, shooting this movie 'Alpha Dog' on the weekends and I was going back and forth between these sets and then it came out.

"My role was kind of revealed to the world and it was the sensational storyline of like queer love between two teenage girls on this like, American soap. At the time I was like, 'Well this should be normal. Why is it such a big deal?' But people either got riled up in a good way or got riled up in a bad way. And I was like, 'Well this is an important conversation.'"