The excessive exercising that is frequently observed in anorexia nervosa (AN) has been viewed both as an addictive behavior and as a type of obsessive compulsive disorder. The present study tested a nonrecursive structural equation model that specified associations among personality factors, cognitions, and behavior in the development and progression of excessive exercise in adolescent patients with AN. As proposed, findings indicated that both addictive personality and obsessive-compulsive personality contributed to excessive exercising by means of their influence on obligatory/pathological cognitions about exercising. Childhood physical activity also predicted excessive exercising. The implications of these results are discussed from a psychobiological perspective.