LESS than a couple of kilometres separate them, but the bustling Portland Street Special Child Care Centre and the room for abandoned handicapped children at Kwong Wah Hospital could be on different planets. The centre in Mongkok is run by the Heep Hong Society for Handicapped Children and provides an ideal model for the mental and physical development of preschool handicapped children. Off a corridor festooned with strings of paper flowers and mobiles, in a brightly coloured room with red mats on the floor, seven members of staff were singing in unison while gently trying to straighten the limbs of severely handicapped toddlers. Carefully, they encouraged the little children in their laps to sit up and support themselves. Some of the toddlers smiled or giggled, prompting their helpers to laugh too. ''When we started this group in September they [the children] cried all the time,'' said Agnes Ng Mun-yee, an occupational therapist at the centre. ''Initially they were so over-sensitive to handling. They were uncomfortable about stretching their limbs and a little bit overawed by all the attention and noise. ''But, after these kinds of activities their tolerance levels are much higher. They are learning to learn. This is the starting point for their training.'' All the children at the centre live at home with their parents, some of whom participate in the therapy sessions by gently pressing their children's feet on to materials of different textures, or by encouraging them to stand. ''It is good for the children to have their parents with them. Some of the children smile when they hear the songs,'' Ms Ng said. ''But often their responses are very small - it might just be a blink of their eye. That's when you really need to know the child.'' These are among the most severely handicapped children at the centre. But the atmosphere is far removed from the antiseptic surroundings of a hospital ward. ''We always try to make the centres as cheerful and as colourful as possible. I would hate people to think it should be gloomy,'' said the society's director, Nancy Tsang Lan-see. ''People should consider these children as students first and handicapped second.'' Hong Kong's 17 Heep Hong centres are subsidised by the Social Welfare Department. Recently it agreed to meet the running costs of a new centre planned for Tai Po, if the society could raise the capital. But, according to Ms Tsang, demand far exceeds supply. There are more than 400 children waiting for places at Heep Hong centres, and approximately 1,500 in need of similar programmes all over the territory. ''The waiting list in the New Territories is particularly alarming. It's a terrible shame because it's such a critical period for these little ones,'' she said. In the corner behind her, on soft mats, four young children were asleep. Many of the children were physically weak, she explained, and the sessions of therapeutic play left them exhausted. ''We try to make use of every minute they are here,'' she added. ''Whether it's eating, walking, playing . . . every moment stimulates them.''