© 2017, Springer Science+Business Media New York. Background: A growing number of studies suggest that bariatric surgery is safe and effective for adolescents with severe obesity. However, surprisingly little is known about changes in dietary intake and eating behavior of adolescents who undergo bariatric surgery. Objective: Investigate changes in dietary intake and eating behavior of adolescents with obesity who underwent bariatric surgery (n = 119) or lifestyle modification (LM) (n = 169). Setting: University-based health systems Methods: A prospective investigation of 288 participants (219 female and 69 male) prior to bariatric surgery or LM and again 6, 12, and 24 months (surgery patients only) after treatment. Measures included changes in weight, macronutrient intake, eating behavior, and relevant demographic and physiological variables. Results: Adolescents who underwent bariatric surgery experienced significantly greater weight loss than those who received LM. The two groups differed in self-reported intake of a number of macronutrients at 6 and 12 months from baseline, but not total caloric intake. Patients treated with surgery, compared to those treated with LM, also reported significantly greater reductions in a number of disordered eating symptoms. After bariatric surgery, greater weight loss from postoperative month 6 to 12 was associated with self-reported weight consciousness, craving for sweets, and consumption of zinc. Conclusions: Adolescents who underwent bariatric surgery, compared to those who received LM, reported significantly greater reductions in weight after 1 year. They also reported greater reductions in disordered eating symptoms. These findings provide new information on changes in dietary intake and eating behavior among adolescents who undergo bariatric surgery.