One of the most serious and painful diseases all over the world is cancer. Despite the progress in preventing, diagnosing and treating cancer, the need for specialised services for people that are diagnosed or that have survived cancer appears to have increased. On the other hand, depressive disorders have been found to be of the most important causes of burden of disease. Depression is not only the most important cause of functional impairment in individuals that suffer from it, but also that especially in cancer survivors it can be a very important cause of non return to work. Approximately half of the cancer patients seem to develop some psychiatric symptomatology. Most commonly they present with reactive depression or a major depressive episode and some times they can even present with delirium. Most of the symptoms, especially following the diagnosis of cancer, seem to be reactive to the diagnosis of the chronic illness. Depression and cancer quite often coexist. The symptoms of the psychiatric disorder can precede, follow or coincide with the diagnosis of cancer. Surveys have shown that this could at times be explained by common biological factors that precipitate the appearance of both diseases. At the same time this could also be explained by psychological or environmental factors that could facilitate the appearance or exacerbate the symptoms of both illnesses. It has also been shown that the presentation of the symptoms of the cancer can complicate the manifestation of the depressive symptoms and vice versa. There are occasions where the cancer can cause depressive symptomatology like for example tumours of the central nervous system. On other occasions the treatment for cancer could cause or exacerbate existing depressive symptomatology. The prognosis of this comorbid condition appears to remain better if both disorders are taken into account and treated simultaneously. Therefore health services should take a holistic approach in the care of the cancer patient.