Background Individuals with body dysmorphic disorder (BDD) are highly distressed due to defects they perceive in their physical appearance that are not noticeable to others. The condition often leads to impaired functioning in relationships, socialization, and intimacy and a decreased ability to function in work, school, or other daily activities. Although BDD seems to be relatively prevalent, it is under-recognized by people in general and by health care professionals. Individuals with BDD are secretive about their symptoms, and they usually do not recognize that they are suffering from a psychiatric disorder. Instead, in an attempt to relieve their symptoms by correcting their perceived defects, they commonly seek dermatological treatment or cosmetic surgery. However, such interventions usually do not result in any decrease in BDD symptom severity, but can rather aggravate the symptoms. Therefore, it is crucial that health care professionals recognize BDD in order to offer adequate care. Prior to the studies conducted for this thesis, there were no known data regarding the prevalence of BDD in Sweden. Main aims (i) To translate a screening questionnaire for BDD (the Body Dysmorphic Disorder Questionnaire, BDDQ) into Swedish and validate the questionnaire in a community sample. (ii) To estimate the prevalence of BDD in the general population of Swedish women and in female dermatology patients. (iii) To explore BDD patients’ experiences of living with the disorder, including their experiences of the health care system. Methods The BDDQ was validated using the Structured Clinical Interview for DSM-IV (SCID) as the gold standard for diagnosing BDD (Study I). The validated BDDQ was used to estimate the prevalence of BDD in a randomly selected population-based sample of Swedish women (n=2 885) (Study II) and in a consecutive sample of female dermatology patients (n=425) (Study III). In Studies II and III, the Hospital Anxiety and Depression Scale was used to assess symp