Superior mesenteric artery (SMA) syndrome is a rare disorder, characterized by compression of the third segment of the duodenum by the mesenteric artery at the level of the SMA, resulting in duodenal dilatation. Precipitating factors of the SMA syndrome include prolonged bed rest, weight loss, abdominal surgery, and increased lordosis of the spine. We report a case of SMA syndrome caused by anorexia nervosa in a 15-year-old adolescent girl. CT and an upper gastrointestinal contrast series revealed partial obstruction of the third portion of duodenum and decreased aortomesenteric distance. The patient`s symptoms were successfully treated with total parental nutrition and psychiatric treatment including supportive, cognitive behavioral therapy and antidepressant medication. This case shows that SMA syndrome is an unusual gastrointestinal complication that may occur in patients with anorexia nervosa. (Korean J Gastroenterol 2011;58:280-283)