The patient was a 49-year-old man who developed a right-sided spontaneous pneumothorax with dyspnea and thus was referred to our hospital. A chest CT scan on admission showed a cavitary nodule in the right lung apex. The pneumothorax was accompanied by a malignant tumor, and a partial resection was performed by thoracoscopy to both treat the pneumothorax and to make a diagnosis of the tumor. A histological examination revealed the presence of large cell neuroendocrine carcinoma of the lung. The cause of pneumothorax was thought to have been a rupture of the wall of the cavitary nodule. A right upper lobectomy with mediastinum lymph node dissection was thereafter performed. No remnant cancer tissue nor lymph node metastasis was observed. The possibility that lung cancer may sometimes include large cell neuroendocrine carcinoma should therefore be considered in patients demonstrating pneumothorax with a tumor.