Siao, 59, says she was inspired by a friend who was raped by a colleague as a teenager and never recovered. 'She told me about it and made me swear not to tell anyone,' says Siao. 'Her whole life has fallen apart ever since the trauma - she hates herself, can never hold on to a job, can't handle any relationship, is unhappily married because whenever her husband touches her she jumps. She's now in her late 60s and still has nightmares about the rape. So I decided to do something to help victims like her.'

There were no organisations dedicated to the issue in Hong Kong, so Siao set one up herself. She went back to college to learn about the subject, taking a master's degree in child psychology in 1998. She then worked at the Queen Mary Hospital as a counsellor and psychologist from 1998 to 2002. Today, Ecsaf is an established charity and regularly attracts famous names to fund-raising events.

Actress Victoria Lam Kin-ming is also well aware that her reputation is the main reason her Joyful (Mental Health) Foundation has been so successful at raising funds. In the past year, the two-year-old charity has raised more then $7.5 million. Like Siao's, Lam's charity is also the first of its kind in its area of expertise, offering counselling to sufferers of depression and emotional disorders and raising awareness of the issue through educational talks and promotional activities. It has established its name quickly, largely thanks to her efforts such as a television fundraiser last year and a charity auction in a shopping centre with actress and TV presenter Carol Cheng Yu-ling.

'Because I've been in this business for more than 30 years, it's easy for me to find the right person for help because I know more people,' says Lam, who has suffered from depression since 2002. 'People are also more willing to talk to me because they know who I am.'

Lam's experience with depression - which left her bed-ridden at one point and contemplating suicide - showed her that there was a lack of understanding about the issue. 'I stayed in bed for five days and didn't even get up to shower or anything,' she says. 'I just didn't know what was wrong with me. Then after I realised it was an illness, I found people misunderstand and think we're simply lunatics.

'After I recovered to a point where I could start functioning again, I asked myself what I could do to help get Hong Kong to understand mental and emotional illnesses better.'

The only organisation to turn to was the Hong Kong Family Link Mental Health Advocacy Association. Lam attended its classes, designed for patients suffering from emotional disorders, and their families. 'I learnt a lot about my illness from them.' The classes ended when the association ran out of funds. That inspired Lam to start raising money herself and today Joyful donates part of the funds it raises to the association.

Not all celebrities choose to work with traditional charities. Film actor Michael Wong, for instance, just wants to give kids a lift. After working with the Hong Kong Air Cadet Corps, he realised that many cadets had never got off the ground. He set up Operation Flying Eagle to give them their first chance to fly. 'I'm passionate about helicopters and started flying the Robinson R44 four-seater in 2001,' he says. 'Two years ago, when I was going to the aviation club I would see children, obviously air cadets, in their uniforms just marching in the car park. I went up to them and said, 'Do you kids get to fly?' and they said 'No, not at the moment'. I thought, this isn't right. I'm off to fly in a helicopter, how selfish is it of me to go up and have all this fun, spend all this money flying with three empty seats?'

This year, Operation Flying Eagle will fly 600 cadets around Hong Kong Island. 'It's all about freedom,' Wong says. 'I think to myself, if I could make just a little bit happen - what a difference that could make to these children.'

Wong wants to extend his operation to underprivileged or disabled children. 'If I can get one kid through the programme and have them go on to become a pilot, then for me the charity has been a success,' he says. 'Celebrities get to move so freely, we get to see so much. I know, for instance, when Jackie [Chan] goes into China and sees the poverty, it breaks his heart. The average person doesn't get to see these things. This is terrible. The contrast is too much.'

Chan established the Jackie Chan Foundation in 1988. Instead of gifts, he asks his fans to send him money, which goes to his charity. Last year, his foundation built 11 schools in rural China. He also helps those who share his passion for performing, whether in the theatre or the sports arena. Susanna Chan Wan-fai, of the Hong Kong Academy for Performing Arts, says Chan plays a key role at the academy. 'Mr Chan is both a donor and an honorary fellow of the academy,' she says. 'But more than this he encourages the students. He's a very busy person, but each year he takes the time to visit and talk to the students. He's also created a scholarship to give children the chance to go to the US and work with film directors, and some of our students have even gone to work for him after graduating.'

Chan is also involved with Lingnan University, donating $4 million to build a gymnasium on its campus.

There's little doubt that the power of celebrity plays a crucial role in the success of many Hong Kong-based organisations. 'We tell the world Jackie is an honorary fellow of the APA,' Susanna Chan says. 'Having an artist of this calibre associated with the academy helps put us on the international stage.'

Additional reporting by Winnie Yeung