The objective of the pilot study is to measure the changes in health-related quality of life (HRQOL, general and prostate specific) 3 months after the disease has been diagnosed in men with prostate cancer. The results are compared with benign prostate hyperplasia (BPH) patients. Also the influence of psychosocial factors (distress, coping and social support) on the experienced changes in health-related quality of life is studied for both patient groups. The sample consists of 61 patients who filled in the questionnaire before the diagnosis was know to them and after 3 months (38 benign prostate hyperplasia and 23 prostate cancer patients). The measures consist of: quality of life, micturation symptoms, sexual functioning, coping style, psychological distress, life events, social support, social desirability, and health behavior. The results show a decrease in quality of life for prostate cancer patient after three moments, while the quality of life measure for BPH patients are stable over time. For both patient groups, the psychosocial factors do not change after 3 months. The psychosocial factors contribute only marginal to the changes in quality of life. Conclusions are drawn concerning the need and the content of psychosocial support and education for prostate cancer patients.