We report a 70-year-old man with prostatic carcinoma presenting as supraclaviculer and mediastinal lymphadenopathy. He had no urinary tract symptoms, and computed tomography and FDG-PET showed no abnormality in the prostate or pelvic lymph nodes. Metastatic prostatic adenocarcinoma was finally diagnosed from the results of immunohistochemical staining for PSA of a biopsy specimen of the mediastinal lymph node, and he was treated by hormonal therapy. There are fears that some other similar cases might be treated with chemotherapy as lung cancer without immunohistochemical staining. Prostatic carcinoma should always be considered in the differential diagnosis of elderly men with supraclaviculer or mediastinal lymph node metastases, since appropriate treatment will lead to a prolonged survival.