Although adolescent dieting is common, comparatively little is known about its developmental course. The present study investigated the self-perception and body shape satisfaction of 9-year old girls and boys in different weight categories. Two hundred and thirteen girls and 166 boys from three schools completed assessments of body-esteem, self-esteem, body shape preference and dietary restraint. The children's body weight and height were also measured. The heaviest children expressed the most discontent, having a low body-esteem, a desire for thinness and higher levels of dietary restraint. However, this desire for thinness and associated dieting motivation was apparent in some children in all weight categories. Furthermore, this pattern was more characteristic of girls than boys. By the age of nine, girls and boys already differ in their body shape satisfaction and differ in their body shape aspirations. Initiatives to reduce obesity should acknowledge these early and strongly-held gender differences or risk promoting the unwarranted pursuit of thinness by girls.