IN her own very understated way Ireland's Saoirse Ronan's has just become one of the most important young actresses in Hollywood. After her Oscar nominated turn alongside Keira Knightley in Atonement earlier this year, Ronan quickly took off for Belfast where she filmed the forthcoming Tom Hanks produced blockbuster City of Ember in a purpose built indoor film studio that was once part of Harland and Wolff's massive shipyard.

No sooner had she wrapped up in Belfast but she was off again to Wellington, New Zealand to star as the heroine of The Lovely Bones, the film adaptation of the bestselling book directed by Lord of The Rings auteur Peter Jackson that's due for release next year.

Her recent film roles have included playing Michelle Pfeiffer's free spirited daughter in the straight to DVD romantic comedy I Could Never Be Your Woman, and she just appeared as Catherine Zeta Jones' daughter in the independent thriller Death Defying Acts that opened in limited release in July.

And next week Ronan will begin shooting The True Confessions of Charlotte Doyle in New York, opposite Pierce Brosnan, with Danny DeVito directing.

Considering all the A-List casting, it's sometimes difficult to remember that she's still only 14. To date only Jodie Foster has notched up so many serious drama roles in big budget films at such a young age, and it's a tribute to Ronan's talent that the young Carlow girl is taking it all in her stride.

"At the end of the day it's just a movie, you know," Ronan says in her distinctly north Dublin accent during a phone interview with the Irish Voice last week. "You can enjoy it and enjoy talking about it but eventually you'll have to move on to the next one."

Making films can be hard work but there's also another side: - the glamour, the fashion, the red carpets and the fabulous six-figure income. The trick for any actor is finding a way to be happy in both worlds.

"When I go home to Carlow everyone has been very supportive and people would come up to me on the street and congratulate me. It's lovely that they do that, but as you know Irish people don't make a big fuss over anyone, you know?

"So it's nice that they wouldn't be all over me the way that happens here. They don't get star struck the way Americans do, which I love. It's just me at the end of the day."

In her latest big budget film, the science fiction fable City of Ember, which opens in October, Ronan plays the film's spirited hero, Lina Mayfleet, a young girl who doesn't automatically accept everything her elders tell her. And although this first marks her out as a teenage tearaway, eventually she ends up saving the lives of everyone around her.

In the new film the people of the city of Ember have flourished in an amazing underground world of glittering lights for generations. But now Ember's once powerful generator is failing, and the great lamps that illuminate the city are starting to flicker. In a race against time, Lina and her friends have to search Ember for the clues that will unlock the ancient mystery of the city's existence and escape to the surface before the lights go out forever.

Says Ronan, "I loved the fact that Lina was so responsible. She doesn't really think about herself she always thinks about her baby sister Poppy and her granny. I also loved the way she runs through the whole movie because I'm really athletic. But the best thing about her is the way she looks for the positive side of whatever she sees."

It's typical of the young Irish actress that she'd gravitate toward an action role involving a distinctly plucky heroine. Spend five minutes in her company and you'll know she'll never be terrifically interested in playing a wilting flower or second fiddle to any man. That kind of spirit makes it easier for her to act alongside Hollywood heavyweights without a thought.

"I met Tim Robbins on the set and he was such a lovely guy, so down to earth. He'd slag you and he'd just be great, you know? And Billy Murray is mad but he's brilliant. I had a good few scenes with him and because he's so funny he kind of lifts the set up a bit when he's there."

Murray has a reputation - particularly among actors - for being difficult to work with, and Ronan has multiple scenes with him in the new film, but she sounded shocked to be asked if he had ever tried her patience. "No! I haven't really had that experience with anyone that I've worked with," she replies, sounding heartfelt.

For Ronan, who spends longer than she would like to away from Ireland each year, the fact that the main scenes of the film were filmed on a massive set built in the old Harland and Wolff Shipyard in Belfast was an opportunity to be in the country and within a stone's throw of home.

"We filmed basically all of it in Belfast in the shipyard where they painted the Titanic. It was huge inside the hanger and they built this massive set with streets and houses. It was brilliant."

Ronan's parents, Paul and Monica, hail from Dolphin's Barn and Cabra in Dublin, and their down to earth approach to life has ensured that Saoirse has remained completely unaffected by all her recent globetrotting. In the 1990s the Ronan's lived in New York, where Saoirse was born, and where her father Paul was first discovered as an actor.

The family moved back to Ireland when Saoirse was three, and later a chance encounter launched her entrance into the entertainment world. Paul went for an audition one day and a talent scout noticed his daughter. Saoirse was just eight years old at the time. Soon she started getting small roles in television, and then her career took off.

Earlier this year Ronan became one of the youngest actors ever nominated for an Oscar for her performance as 12-year-old aspiring writer Briony Tallis (a character she didn't like, as it happens) in Atonement, the film based on Ian McEwan's bestselling novel. The Best Supporting Actress Oscar nod marked her entrance into the big leagues, but Ronan remains true to herself.

"I'm going home to Ireland tomorrow, I'm heading back to Carlow for a week and then I'm coming back to New York to do The True Confessions of Charlotte Doyle with Pierce Brosnan, with Danny DeVito directing," she says.

"Sometimes I do miss out on just being at home and hanging out with the other kids, but I'll get to do that next week so it's not too bad. I can't wait to work with Pierce Brosnan. In the new film he's playing Captain Jagger, a really horrible ships captain, which is far from the type of character he usually plays. You wouldn't expect him to play a role like this at all. I saw him in Mamma Mia! back in Carlow last month. He's not a bad singer, he's all right. It was a good old laugh that film, wasn't it? "

City Of Ember opens nationwide on October 10.