Uma Thurman knows she has been bad. Her blue eyes betray her. She blushes, a gentle pink. She has taken up smoking again ...

"I'll have to stop this," she says, squirming and laughing. "I haven't smoked in three years. This lapse is an appalling fall from grace. It's horrible." She has a look of hangdog guilt, and she asks for a light.

Thurman is not a conventional beauty. She possesses a sensuality that smoulders from the screen. In the flesh she is mesmerising, even with a cigarette in her hand.

Thurman took up the evil weed again at the recent Cannes Film Festival. It helped her through the incessant round of media interviews for the two films she starred in which premiered at the festival. "A lot of people go nuts in this business. Partly it's to do with how you metabolise your stress. I'm not too good at it. I go in and out of diets. When I was making Pulp Fiction, it was all brown rice. Nowadays I'm bouillabaissing it and on The Golden Bowl I developed a penchant for exotic desserts."

The Golden Bowl, a typically sumptuous Merchant Ivory period piece, and Vatel were the films Thurman was promoting at Cannes. While the former sees her kindling a flame for Jeremy Northam as a lovelorn Charlotte, in the latter she plays a vulnerable courtesan at the court of Louis XIV, opposite Gérard Depardieu as a royal celebrity chef. She's also to be seen in Woody Allen's new movie, Sweet and Lowdown. Despite this triumvirate of new films, the 30-year-old actress says she has become much more selective about her work. Since the disastrous remake of The Avengers, Thurman has been busying herself looking after her daughter with her husband, Ethan Hawke. Maya Ray is now almost three years old, and has significantly changed Thurman's priorities.

"My career used to be 100 per cent the most important thing in my life, but that's not the case any more. Once you have a child you tend to be busy forever. It seems like I never sleep. Certainly there's not been much of it for the last three years but I guess any woman who's a mother and also working finds that," she says. "Some sense of perspective has snuck up on me but I feel secure about the work. I try to be a lot more selective, otherwise I'd be working all the time. Desperation is the perfume of the young actor. It is so satisfying to get rid of it."

Now happily basking in domesticity in Manhattan, Thurman says it takes time to return to reality after playing an emotionally demanding role. She finds it easier with the advent of family life. "Now I have my daughter I am always being brought back to earth the moment I walk through the door. When I was younger I think my attempt not to fit into a Hollywood niche may have been detrimental. It was a problem because it affects your 'castability'. You do not seem an obvious choice for anything because you do a little of everything. And we all know that in Hollywood often you need to be the obvious choice. Over time, though, it has worked because I feel well-rounded and confident on different fronts. I am happy to go into different genres - from comedy like the Woody Allen to serious drama or a stylised piece."

Although she had reservations initially about playing the heroin-addicted moll in Pulp Fiction - which won her her first Oscar nomination - she was quickly persuaded otherwise. "Pulp Fiction was important. Quentin [Tarantino] and I had a remarkably creative relationship. It was the first time I had worked with someone who was roughly my own age. It was definitely fun." It was even more fun to work with Hawke, whom she met first at a party before they worked together on Gattaca, when their relationship blossomed. Hawke recently directed her in a low-budget ensemble drama shot digitally. They hope to repeat the trick with a project they are developing from a play about a bunch of New Jersey girls who want to get married.

When she's not working, Thurman admits to being "a lady who likes to have lunches". Otherwise she's happy to dabble in her garden and hang out with her daughter. She claims to be a little lazy, although it's difficult to believe her.

Thurman has come a long way from when, aged 18, she portrayed the virginal girl seduced by John Malkovich in Dangerous Liaisons. She appeared to be the stuff of male fantasies, a fact which had reared its way into the open when she spent time as a model during a summer break from school. She recalls now that it was "a really uninteresting way to spend time".

"The basic philosophy was along the lines of: 'Buy more stuff and you will look ten years younger,' or 'Guys will like you if you wear this'. I was never very good at convincing people they needed more stuff."

From there, she progressed to be one of the more memorable aspects of Henry and June as Henry Miller's bisexual Brooklynite wife; she put Kim Basinger in the shade in the Richard Gere thriller Final Analysis and, in another thriller, played an isolated blind girl under siege in Jennifer Eight with Andy Garcia. She also acquitted herself well in Gus Van Sant's Even Cowgirls Get the Blues, then put herself in the feminist firing line as a call girl in John McNaughton's Mad Dog and Glory.

Early in her career, Thurman was ill-prepared to cope with so much close attention, despite her rather unconventional upbringing. Her Swedish-born mother Nena was a psychotherapist; her father Robert was one of the first Americans to be ordained as a Tibetan Buddhist monk. He currently works as head of religion at Columbia University. She has three brothers, Dechen, Ganden and Mipam, all named after Hindu deities. Uma translates as "bestower of blessings". Her state of well-being was not helped by a personality-hungry media.

The response at the time forced her to retreat into the anonymity of her home in New York, which she had fled at the age of 15 in a fit of what her mother described as "typical teen restlessness". She earned a living by washing dishes and modelling - which her mother had done decades earlier. She was married for all of 18 months to Gary Oldman, who was ten years her senior. They split amid rumours of his excessive drinking. Then she took up with her co-star from Beautiful Girls, Timothy Hutton, before Hawke walked into her life.

Thurman insists she has no ambition to create an image for herself, content to leave such artificial hyping to the likes of Julia Roberts or Sandra Bullock. She lacks vanity, she says, claiming to be unaffected by the effect of her looks and has become more philosophical about the highs and lows. In her more tender years, she would have run off and hidden from the flak. Today she is more than prepared to face the music.

"My ambitions have been raised as I have less to lose. I feel I could do anything and if people don't like it, then I'll go on to try something else. You see your friends go up and down the ladder, but it's such a temporal way to look at things. If you're a slave to the fame game then it's a really ugly universe. That's not my mission - and I feel fantastic." Once she eschews the evil weed once more, Uma Thurman will have reached Nirvana.

Sweet and Lowdown is released on 9 June, he Golden Bowl in October and Vatel later in the year.