Female patient, 21 years of age, with diabetes mellitus type I, admitted due to progressive weight loss, with a recent history of impaired glycemic control, ketosis and amenorrhea for 12 months. Studies were conducted in order to exclude an endocrine or malignant disorder. After nutritional, endocrine and psychiatric evaluation, the diagnosis of anorexia nervosa, was made. Therapeutic results and clinical course after the first year are shown. The case raises important problems, especially within diabetic population, puzzling the clues for diagnosis and therapy.