Objectives: This study aimed to examine the association between sitting time and BMI-defined low weight and overweight/obesity in Korean adolescents. Methods: Data were from Adolescent Health Behavior Online Survey (KYRBS) in 2015 including 63,345 adolescents aged 12-18 years. The analysis investigated low-weight and overweight/obesity odds ratio(OR) according to study sitting time and leisure sitting time adjusted for sex, school grade, social-economic status(SES), physical activity and sleeping time. Results: After adjusting for sex, school grade, SES, physical activity and sleeping time, study sitting time and leisure sitting time were not significantly associated with low-weight. However, leisure sitting time was positively associated with overweight/obesity. Conclusions: Health program to less sitting time should be established with consideration for differences in risk according to sex, age, SES and active leisure time through the school physical class should be provided to adolescents. Additionally, strategies to promote healthy weight are required to integrate sitting time, physical activity and sleeping time in Korean adolescents