In bullous lung disease the incidence of lung cancer occurs with significant frequency among the general population, but lung cancer with a spontaneous pneumothorax is rare, and the prognosis is frequently poor. Five cases of lung cancer with emphysematous bullae of the lung were reported. In 4 cases there were simultaneous occurrences of lung cancer and pneumothorax. The patients were 49-, 36- and 68-year-old men and a 72-year-old woman, and the initial sign in all was pneumothorax. Histologically, there was one squamous cell carcinoma, two poorly differentiated adenocarcinomas and one well-differentiated adenocarcinoma. In the other case, giant emphysematous bullae were diagnosed in a 51-year-old man and were treated by bullectomy. Histological examination incidentally revealed a small well-differentiated adenocarcinoma, which extended along the wall of the largest right bulla. About 18 months later, the patient was found to have poorly differentiated adenocarcinoma of the left lung, which was treated surgically. We should always be careful of lung cancer associated with emphysematous bullae and pneumothorax.