Obesity continues to be a major public health issue. In adolescents, there are limited studies on the relationship between obesity and sleep duration. We found hypothesized that an average sleep duration of <6 h in adolescents was associated with obesity. Data were from the National Longitudinal Study of Adolescent Health (ADD Health); a survey of 90,000 youths, aged 12-18 years; surveyed in several waves. The sample population for our study was 13,568. Weighted multiple logistic regression was used to identify the relationship between obesity at Wave II and sleep duration, having adjusted for skipping breakfast ≥ 2/week; race, gender, parental income, TV ≥ 2 h per day, depression, and obesity at Wave I. At Wave I, the mean age was 15.96 ± 0.11 years; mean sleep hours were 7.91 ± 0.04. At Waves I and II, respectively, 10.6 and 11.2% of adolescents were obese. Adjusted analyses suggest that the effect of shortened sleep duration in Wave I was not significantly predictive of obesity in Wave II (P < 0.218). Longitudinally, depression and TV ≥ 2 h per day at Wave I was associated with a higher risk of obesity at Wave II in adjusted analyses. Depressed adolescents were almost twice as likely to be obese (OR = 1.84, 95% CI = 1.25-2.72); adolescents who watched TV ≥ 2 h per day were 37% more likely to be obese (OR = 1.37, 95% CI = 1.09-1.72). Environmental factors including TV ≥ 2 h per day and depression were significantly associated with obesity; shortened sleep duration was not. Future longitudinal studies in adolescents are needed to determine whether timing of television watching directly influences sleep patterns and, ultimately, obesity.