Mucoepidermoid carcinoma arising in the tracheobronchial tree is an extremely rare tumor. Usually it remains as locally invasive neoplasm, although malignant change is described. Histologically, it is characterized by an admixture of vacuolated, mucus producing cells and sheets of epithelial cells with a cohesive pattern which resemble squamous cells. Its clinical and histopathological behaviors were reported as varying degrees of benign to extremely malignant. We had experienced two young patients with low-grade mucoepidermoid carcinoma of the right and left upper lobar bronchi. A 15-year-old man who had had intermittent hemoptysis for 1 year underwent right upper lobectomy. And the other 18-year-old man had suffered from obstructive pneumonitis for 6 months underwent left pneumonectomy. The postoperative courses were uneventful, and the bronchoscopy and chest CT which were done at 6 months later revealed no regional recurrence.