A 64-year-old man with a history of smoking was admitted to our hospital, because he was noted to have a solitary mass lesion at the apex of the right lung on a chest roentgenogram. Eight months before admission, he had come to our hospital because of hemoptysis. At that time, however, no abnormal shadow was seen on his chest roentgemogram, except for multiple bullae at both apexes. Based on chest CT findings on admission, the tumor appeared to be a hematoma growing inside the bulla. The resected tumor was found to contain a large amount of coagulated blood in the bulla. Histopathological examination of the bulla revealed a proliferation of large atypical cells from the inner surface of the bulla toward the inner space. Thus, the diagnosis was large cell carcinoma within the wall of the pulmonary bulla, the inside of which was filled with hematoma. We believe that the hematoma in the bulla allowed us to make an early diagnosis, and thus to succeed in curing the patient.