An asymptomatic 43-year-old female was admitted to the Hospital because of an abnormal nodule in the left lung field on screening chest X-ray. Chest CT showed a tumor shadow mass (4 x 3 cm) in the left lower lobe. Bronchofiberscopy revealed an endobronchial polypoid mass obstructing the lower lobe bronchus at the orifice of left B10. Lt lower lobectomy was performed. Histopathological examination of the specimen showed the tumor (4.5 x 3.6 x 3.6 cm) developing not only within the tracheal lumen, but also in the lung tissue. Because immunohistochemical staining for desmin and alpha-smooth muscle actin was positive, we diagnosed leiomyoma. As MRI revealed multiple uterine masses after operation, we discussed the diagnostic problems in the relation to metastasizing leiomyoma of the uterus.