Background: Previous findings on psychological problems and disorders in former West and East Germany have been inconsistent. This can primarily be explained by different study methods (questionnaire, interview, expert ratings). Representative studies using established valid and reliable interviews for diagnosing mental disorders are still missing. Objectives: To compare 1. prevalence of mental disorders and 2. quality of life in West and East Germany. Methods: Presented data come from the Mental Health Supplement of the German National Health Interview and Examination Survey (GHS-MHS; representative sample; age 18-65; N = 4,181) conducted in 1998/99, using the M-CIDI-interview to assess diagnoses of mental disorders according to DSM-IV. Health related quality of life was assessed with the SF-36. Results: 12 month prevalence was 32% in West and 28% in East Germany (lifetime: 44% vs. 38.5%). Taking different sociodemographic characteristics and somatic health status into account, comorbidity as well as the following disorders are more prevalent in West Germany: substance use disorders, unipolar depressions, social phobia, somatoform and eating disorders. Furthermore, there is a tendency to show poorer health related quality of life in the West, whereas in some other areas regarding quality of life East Germans score little (but significantly) lower than West Germans. Conclusions: Contrary to some former results and theoretical considerations, rates of mental disorders in former East Germany are actually lower as compared to the West. The results confirm that prevalence estimates of mental disorders are rather stable and robust across regions and societal influences.