Gwyneth Paltrow credits laughter for her successful marriage.

The Oscar-winning actress has been wed to Coldplay frontman Chris Martin for almost nine years and she says sharing a similar sense of humour is part of the reason they're still together.

Gwyneth - who has two children, Apple, eight, and six-year-old Moses, with Chris - said: ''We laugh a lot, and at the same jokes. We like the same music and we like to do the same things.''

However, the 39-year-old beauty admits having similar personalities is not always a good thing.

She told America's InStyle magazine: ''Our artistic temperaments together [is the hardest part]. Artists are sensitive. There are ups and downs, mood-wise. Musicians need a certain gravitas and focus in order to write. The temperament that goes with someone who is creative can be challenging.''

Gwyneth also revealed the couple haven't ruled out having more children although she admits it might not happen.

She said: ''My brain says, 'Oh, I think I'm done, the kids are so big now, and I don't want to go back to changing diapers.' But a part of me would love to have another. Of course, I'm old now!''