This study investigated the association between the weight status of middle school students and the various weightrelated characteristics including desired weight, weight perception, weight-related practice, physical activity, and overeating behavior. Questionnaires were administered to 473 middle school students (178 boys and 295 girls) in Daejeon. Boys and girls were divided into three groups respectively; (1) underweight (BMI < 5th percentile) (2)normal weight (5th percentile < or = BMI < 85th percentile) (3) overweight (BMI > or = 85th percentile). Using BMI calculated from measured height and weight, 14.0% of boys and 6.8% of girls were underweight, and 16.3% of boys and 14.2% of girls were overweight. However, among this sample of students, 38.4% of boys and 13.6% of girls perceived themselves as underweight and 29.4% of boys and 44.9% of girls perceived themselves as overweight. We found that overweight students reported their body weights lower and their heights higher compared to nonoverweight students, resulting in an underestimation of BMI. Based on desired BMI, 79.9% of the girls desired to be underweight and 73.0% of the boys desired to be normal weight. Overweight or normal weight students were less satisfied with their body weights than underweight students. Girls had more weight control experience and concern compared to boys. Overweight girls spent longer times in watching TV compared to non-overweight girls (p < 0.001) and had more overeating behaviors (p < 0.05). Overweight students reported that they ate snacks less frequently than non-overweight students, which may be due to their tendency to report less eating. In conclusion, significant gender differences and weight status differences existed in weight perception, weight satisfaction, and weight control experience and concern. Because perception of overweight is likely to lead to unhealthy eating behaviors and weight control, efforts for adolescents to improve accuracy of weight perceptions and to understand the benefits of being healthier are needed.