Objective: There is a high prevalence of psychiatric disorders, especially depression and anxiety, among cancer patients. If they are left untreated, especially depressive disorders, they may result in poor treatment compliance, increased hospital stays and reduced quality of life. The aim of this prospective study is to investigate the prevalence of psychiatric morbidity among cancer patients and the factors that predict psychiatric morbidity. Method: One hundred and fifty patients with the diagnosis of cancer who were treated in different departments of the Pamukkale University Hospital were included in this study. Psychiatric diagnoses were made according to the criteria of DSM-IV with the SCID-I interview. In addition, all patients were evaluated using the General Health Questionnaire (GHQ) and the Hospital and Anxiety Depression Scale (HADS). Results: 28.7% of cancer patients were found to have a DSM-IV Axis I diagnosis. The most common diagnoses were adjustment disorder with depressed mood (14%) and major depressive disorder (11.3%). Female gender, awareness of the diagnosis of cancer, history of previous premorbid psychiatric disorders and stress factors were correlated with psychiatric morbidity. Conclusion: In this study, the most common diagnoses were adjustment disorder with depressed mood and major depressive disorder, suicidal ideations were also frequently found. Awareness of the nature of the illness, female gender and the duration of the illness were the parameters which predicted psychiatric morbidity. Careful attention should be paid to cancer patients in order to diagnose and treat their psychiatric disorders. Furthermore, two screening instruments (GHQ and HADS) performed satisfactorily for screening of psychiatric disorders in cancer patients.