Attachment insecurity and difficulty with mentalization are common in patients with eating disorders and might be related to their symptoms and lack of autonomy.<br/> AIM: To investigate the role of attachment and mentalization in the course of anorexia nervosa (AN) and bulimia nervosa (BN).<br/> METHOD: Patients with AN and BN were assessed at the start of treatment, and after 1 year and 1.5 years concerning attachment security and mentalization in relation to eating disorder and co-morbid symptoms and autonomy. The results at the start of treatment were compared to those of controls without an eating disorder.<br/> RESULTS: Attachment insecurity and low level of mentalization were more prevalent in patients than in controls, and associated with borderline personality disorder and/or self-injurious behaviour. Attachment security increased after 1 year of treatment. Recovery from eating disorder after 1 year was related to higher level of mentalization and improvement of autonomy. Low pre-treatment level of mentalization predicted persistence of eating disorder until 1.5 years of follow-up.<br/> CONCLUSION: Good mentalization is associated with recovery from eating disorder. More research on the effect of mentalization based treatment for patients with eating disorders, with or without borderline personality disorder, is recommended.