The purpose of this study was to investigate gender differences in behavioral characteristics and their awareness of obese school children. The results were as follows 1. In comparison with eating habits and food preference, the girls had more irregular breakfast and were likely to have vegetables / fruits than the boys. 2. In characteristics related to exercise and activities, boys did more exercise than girls. Particularly, in lunch free time, boys participated in playing various active excercise with friends, but girls participated in more non-active behaviors (such as, chattering, reading, or playing jack-stones). 3. In comparison with their awareness related to obese persons, about a half of boys had positive opinions (e. grong, healthy.), but about only 20% of girls had positive opinions.