PURPOSE: The purpose of this study was to analyze differences in health behaviors among adolescents in order to provide fundamental data to develop an effective body weight control program. METHODS: Secondary analysis was done using data from the 9th (2013) Online Survey on Ado-lescents' Health Behaviors by the Korea Centers for Disease Control and Prevention. The adolescents were divided into low weight, normal weight, overweight, and obesity groups according to body mass index (BMI). Differences in health behaviors were analyzed. RESULTS: Gender, grade, socioeconomic status, perceived-health status, exercise, breakfast, fast food, ramen noodles, snacks, carbonated soft drinks, fruits and vegetables, satisfaction with sleep, stress, smoking, and alcohol consumption were significantly different among the groups. Ingestion of carbonated soft drinks and snacks was significantly higher in the low weight group compared to the normal weight group. Eating fast foods, ramen noodles, and snacks was significantly lower in the overweight and obesity groups compared to the normal weight group. CONCLUSION: Findings indicate that health behaviors among the groups differ from traditional knowledge about obesity. To develop optimal programs and improve efficacy, prior knowledge should be used to think differently and individualized programs should be based on an understanding health behaviors of adolescents.