A turning off the main corridor of the Llandough Hospital near Cardiff leads into a short, brightly painted tunnel. This opens into a room abuzz with children playing on state-of-the-art computers, watching cartoons on a giant TV or wrapped up in Nintendo games.

No doctors or nurses are allowed in here and sick children can play to their hearts' content without fearing that anyone might stick a needle in them. This is the Starlight Express Room, a virtual reality play centre, which opened in Llandough last week. It is the first of its kind in Europe and the largest in the world.

The Starbright Foundation, founded 12 years ago and backed by celebrities such as the actress Emma Samms and Sir Cliff Richard, has already raised money to help to build similar rooms in California and Sydney. Research there had shown that children became so engrossed in the equipment that they forgot their pain and stress and needed significantly fewer drugs. The rooms also seemed to relieve the fear and isolation felt by children confined to hospitals. In Los Angeles, children using "pain pumps" (to administer their own painkillers when needed) used them far less when playing in the room.

"One doctor said that they used less of the drugs, which meant they felt less nauseous. With less nausea, they ate more - as they ate more, they got stronger," says Pat Ryan, the Llandough project co-ordinator, who helped to raise the pounds 160,000 for the new room.

Equipment includes two Nintendo games, six computers with a range of software (from educational to virtual reality games and simulated flights and rides), a large TV with satellite cartoon channels, a closed-circuit television camera and a hand-held camera with which the youngsters can make their own films. The Starlight Express Fun Centre trolley, equipped with TV, video and a game console, can be wheeled to the bedside of a child who is too ill to go to the room.

American research has shown that rooms like this are particularly popular with children who have illnesses which involve painful treatment like chemotherapy, who were also likely to suffer stress and anxiety, and children with long-term illnesses who became bored with being in hospital and cut off from their friends.

"The reaction has been brilliant," says Justine May, a play therapist and one of three full-time staff. "The idea is that it takes them right away from the hospital environment. We don't even wear nurses' uniforms. Playing is important to them. It takes their mind off all their anxieties. Children used to sit in their beds dreading the treatment, getting more anxious as they watched the doctor get nearer to their bed. But now treatment is something they want to get out of the way so they can come in here."

Mrs Ryan's daughter, Julia, a Starlight Foundation volunteer, has visited the American rooms: "You could notice the difference in the children. I was in hospital as a child and I was bored stupid. Trends and fashions pass you by and no kid likes to feel stupid in front of other kids because they have not played a Nintendo game or reached the same level as their friends."

Children may also bring their parents and brothers and sisters in with them. "We try to make it as much like home as we can. You can sit with them on your lap and watch a cartoon, which is what you would do with a sick child at home," explains Polly Smith, a play therapist.

The aim now is to build a second Starlight Express room, probably in the South-east, and to link the two so that children can talk to each other.

In America, the Starbright Foundation, chaired by the film director Steven Spielberg, has launched an appeal to build a research centre and world headquarters for the charity. Coca-Cola has already donated a pounds 6m former film studio site and the aim is to link Starlight Express rooms around the world so that the children can play and talk together. Says Mrs Ryan: "If a child is just starting a long and difficult treatment in Sydney, he can talk to a child in Wales or Los Angeles who has had the same treatment. That child can tell him: 'I've had that, I am better now and I'm going home'."