Purpose of this multicenter epidemiological study was to detect the 4-week-, 12-month-, and lifetime prevalence rates of comorbid mental disorders and to further assess psychological distress in cancer patients across all major tumor entities within the in- and outpatient oncological health care and rehabilitation settings in Germany (Mehnert et al. 20121). Using a proportional stratified random sample based on the nationwide incidence of all cancer diagnoses in Germany, 4,200 patients (68% participation rate) were included in the study, 2,141 (53%) of whom were randomly assigned and interviewed using the oncology-specific adaption of the Composite International Diagnostic Interview (M-CIDI-O). In addition, valid self-report measures covering distress, anxiety and depression were used. Patients were enrolled from acute care hospitals, outpatient cancer care facilities, cancer rehabilitation centers and clinics in five major study centers in Germany. Fifty-one percent of the participants were female; the mean age was 58 years (range 18-75). The most prevalent tumor sites were breast (22.5%), prostate (15.8%), colon (12.7%), and lung (8.2%). Our findings show that the most frequent mental disorders across all tumor entities were anxiety disorders (4-week-prevalence: 13.5%, 12-month- prevalence: 18.5%), followed by affective disorders (4-week-prevalence: 8.5%, 12-month- prevalence: 15.6%) and somatoform disorders (4-week-prevalence: 5.6%, 12-month- prevalence: 10.3%). Using self-report measures, 23.9% of the participants had moderate to severe depression (PHQ-9) and 14.2% had moderate to severe levels of generalized anxiety disorder (GAD-7). However, 51.9% of the patients were classified as having high levels of overall distress (Distress-Thermometer). The impact of sociodemographics and tumor entity will be analyzed. Our data provide an important basis for the implementation of both information and psychosocial support offers and interventions in different health care settings. The identification of predictors for mental disorders in cancer patients allows an early and specific assignment and referral of those patients to adequate psychosocial support.