An 87-year-old man was admitted complaining of cough after he had been treated with drugs at another hospital. Chest X-ray revealed multiple nodules, and chest computed tomography (CT) showed metastatic lung tumors. Abdominal CT revealed staining of the outer portion of the prostate by contrast medium, though this finding was considered nonspecific and nondiagnostic. A CT-guided biopsy of a lung tumor was performed, and the lung tumor was found to be positive for prostate-specific antigen (PSA). Prostate carcinoma was diagnosed by prostate biopsy, which yielded the same findings as the lung tumor. The serum PSA level was high. No metastases except for pulmonary lesions were observed on a bone scintigram and abdominal CT. Prostate carcinoma with pulmonary metastases alone was therefore diagnosed. The present case represents a rare case of pulmonary metastases without any other metastases.