Mental disorders are common in the group of candidates for bariatric surgery, and their complex and heterogeneous nature justifies conducting a psychological consultation in the initial period of selection for surgical treatment of obesity. Untreated mental disorders may be one of the important factors explaining weight regain in patients undergoing bariatric surgery. In order to optimize the surgical treatment of obesity, it seems important to implement an appropriate psychological evaluation in diagnostic and therapeutic procedures. It is particularly important to identify such candidates who require extended therapeutic procedures, including pharmacological and/or psychotherapeutic treatment before starting the procedure. The aim of the study was to discuss the case of a patient with an eating disorder and co-occurring personality disorder, who relapsed after surgical treatment of obesity.