Cancer patients often suffer from major depression or depressive syndromes. Although it is well known that depressive symptoms can appear at any time during the course of an oncological disease, certain periods for instance time after diagnosis carry a higher risk. Reported prevalence rates differ widely (up to 60%), reflecting also diagnostic difficulties. Oncologists recognize depression in their patients only in 15 to 50% and the percentage of patients who receive adequate therapy is even lower. Consequently, this leads to a reduced quality of life. Furthermore, impaired compliance/adherence and consequently a poorer prognosis of the oncological disease are discussed in this context. It should be also emphasized, that concomitant depression increases the risk of suicide in cancer patients. Although the number of clinical trials using either psychotherapy or antidepressant medication for the therapy of depression in cancer patients is limited, good therapeutic options are available.