This large population-based study focuses on the prognostic role of increasing age and co-morbidity in cancer patients diagnosed in the southern Netherlands. Data of patients diagnosed between 1995 and 2002 and recorded in the population-based Eindhoven Cancer Registry were used. Older patients (with serious co-morbidity) with non-small cell lung cancer or prostate cancer underwent surgery less often than younger patients. Elderly with stage III colon cancer, small cell lung cancer, FIGO II or III ovarian cancer or non-Hodgkin's lymphoma (NHL) received (adjuvant) chemotherapy less often, probably because of the higher rate of haematological complications. Administration of adjuvant radiotherapy decreased with age and co-morbidity in patients with rectal cancer, limited small cell lung cancer or breast cancer. In general, elderly did not suffer from more complications than younger patients, except for cardiac complications (colorectal cancer and NHL) and postoperative death (non-small cell lung cancer). For most tumours relative survival was lower for the elderly, except for patients with colon cancer, prostate cancer or indolent NHL. Co-morbidity had an independent prognostic effect, except for tumours with a very poor prognosis. Future prospective studies should investigate whether the guidelines for cancer treatment should be adjusted for elderly with serious co-morbidity.