Primary leiomyosarcoma of the lung is very uncommon, and fewer than 50 cases now have been reported. Primary leiomyosarcoma of the lung resembles bronchogenic carcinoma in its clinical presentation and radiologic appearance. However, the former has some differences; younger onset than bronchogenic carcinoma, polypoid endobronchial growth, few positive cytologic examination of sputum and unusual lymph node metastasis. We experienced a case of primary leiomyosarcoma of the lung.