BACKGROUND: Diet and weight concerns are commonplace and almost accepted features of life for girls during adolescence. Until recently, younger age groups haue largely been ignored, as these concerns were thought to be a product of pubertal development and sexual maturity. Girls under the age of fifteen therefore, have been assumed to be free of the pressures experienced by adult women. However, this belief is now hard to sustain. The object of the present study was to investigate the self-perception and body shape satisfaction in different weight categories of boys and girls aged 12-years old in Korea. METHODS: In May, 1995, one hundred and sixty seven boys and one hundred and twenty girls from two schools in Seoul completed assessments of body-esteem, self-esteem, body shape preference. The children's body weight and height were also measured. RESULTS: The heaviest children expressed the most discontent, having a low body-esteem, a desire for thinness. By the age of 12, girls boys already differ in their body shape satisfaction and differ in their body shape aspirations. There was a significant effect of weight category on the children's body esteem(boys(P =.005), girls(P=.0001). Children in both extreme categories, under-and over-weight, had lower body-esteem scores than those in other weight categories. However, it was the overweight children who had the lowest. reported body-esteem. Body esteem was highest among girls in the 'slightly underweight' category and highest among boys on the 'average weight' category. There was no effects of either weight category or gender on the childrens appraisal of self-esteem. A comparison of the points chosen on the silhouette scales to reflect current and preferred body shapes revealed clear gender differences. Of the girls, 63% placed their preferred body shape at a point thinner than their currently perceived shape, while only 15% chose a broader figure. In contrast,, 41% of the boys rated their preferred figure as broader than their current perception, and 37% as thinner than their current perception. CONCLUSIONS: This study has noted a relationship between body weight and self-perception in 12-year old children. The heaviest children expressed low body-esteem, a desire for thinness. This pattern was more characteristic of girls than boys. Even at this age, well before they have completed physical maturation, girls are aspiring to a body shape which is thinner than their average. This discontent experienced by the heaviest children on this sample was apparent in their lower body-esteem and the distance between their current and preferred body shapes. The girls preference was for thinness, while in the boys it was for a body shape which was broader than their current shape. From their responses, it would appear that the boys' desire was not for fatness, but for a more athletic and muscular build.