Objective Despite the increasing recognition in clinical practice of body image problems in other than appearance related mental disorders, the question remains how aspects of body image are affected in different disorders. The aim of this study was to measure body image in patients with a variety of mental disorders and to compare scores with those in the general population in order to obtain more insight in the relative disturbance of body image in the patients group compared to healthy controls. In a further exploration associations with self-reported mental health, quality of life and empowerment were established as well as the changes in body image in patients over time. Methods 176 women and 91 men in regular psychiatric treatment completed the Dresden Body Image Questionnaire, the Outcome Questionnaire, the Manchester Short Assessment of Quality of Life and the Mental Health Confidence Scale. Measurements were repeated after four months. Results Patients with mental disorders, especially those with post-traumatic stress disorder (PTSD), scored significantly lower on body image, with large effect sizes, in comparison with the healthy controls. Scores of patients from different diagnostic groups varied across domains of body image, with body acceptance lowest in the group with eating disorders, and sexual fulfillment extremely low in PTSD. Vitality did not differ significantly between the various disorders. Gender differences were large for body acceptance and sexual fulfillment and small for vitality. Associations of body image with self-reported mental health, quality of life and empowerment were moderate to strong. After four months of treatment positive changes in body image were observed. Conclusions Negative body image is a common problem occurring in most patients with mental disorders. Diagnosis-specific profiles emerge, with PTSD being the most affected disorder. Body acceptance and sexual fulfillment were the most differentiating aspects of body image between diagnoses. Changes in body image occur over the course of treatment.