Carbohydrate-deficient transferrin (CDT) is a commonly used biomarker for alcohol abuse; however, recent findings questioned its diagnostic value in catabolic subjects. We have thus investigated possible changes of CDT in patients suffering from eating disorders. Retrospectively, CDT values of patients with eating disorders were identified. Twenty-four non-alcoholic subjects could be found, in which CDT was determined at least once during stationary psychotherapy. Anorexia nervosa patients had pathological CDT concentrations in 57% of cases; conversely, bulimia nervosa patients had normal CDT. Patients with initially elevated CDT tended to be more seriously ill than those without. During therapy, the body mass index of anorexia nervosa patients normalized, paralleled by declining CDT. In anorexia nervosa patients, CDT is unsuitable as a marker of alcohol abuse, but it might serve as a parameter indicating prognosis and disease severity. However, case-control studies with larger samples are warranted.