Rachel McAdams always stays friends with her ex-boyfriends.

The 'Vow' actress - who has been in a relationship with Michael Sheen for 18 months - feels ''tenderness'' towards her former partners, which include Ryan Gosling and Josh Lucas, because of the things they have taught her.

She said: ''Am I still friends with my old boyfriends? Yes, absolutely. There's no one who's ever been significantly in my life for whom I don't have a sort of tenderness because they helped to shape who I am.

''However long someone is in your life, they're there to teach us something and I try to make the most of any relationship.''

The 33-year-old beauty values humour most in a boyfriend and she thinks it is particularly important to be able to laugh at problems.

She added to Britain's HELLO! magazine: ''First and foremost, a sense of humour [is attractive]. You can have passion, you can have interests in Common and all the other good things. But if it's to be a long-term relationship, then you're going to need something to get you through the trials and tribulations.

''The ability to laugh together and not take anything too seriously is essential. It's a way to connect that forgives a lot of other things and it allows you to move on much more quickly if there's a problem.''