A 54-year-old man with pulmonary non-tuberculous mycobacteriosis( pulmonary NTM) who had been treated by antituberculous chemotherapy, developed a new nodule of 1.3 cm in size in the segment 1/2 of the right upper lobe. The cavity of 3.5 cm in size in the segment 6 of the right lower lobe from which Mycobacterium intracellulare was bronchoscopically detected, was suspected to be pulmonary NTM lesion. Since lung cancer was highly suspected by radiological examinations, right upper lobectomy and S6 segmentectomy were performed. Pathological diagnosis for the right upper lobe nodule was adenocarcinoma.