Abstract: Objective To compare the computed tomography (CT) manifestations of non-tuberculous mycobacterium （NTM） pulmonary diseases caused by Mycobacterium avium-intracellulare complex (MAC) and Mycobacterium abscessus. Methods The CT findings of 16 patients with MAC pulmonary disease and 15 patients with Mycobacterium abscessus pulmonary disease confirmed by clinical and laboratory test who admitted in Beijing Chest Hospital, Capital Medical University from Jan. 2011 to Oct. 2013 were reviewed retrospectively．CT and high resolution computed tomography (HRCT) findings of all patients were analyzed. χ² test was used to analyze the difference of imaging between MAC and Mycobacterium abscessus pulmonary disease.  Results CT manifestations of air space consolidation (28/31), bronchiectasis (28/31), centrilobular nodules or “tree in bud” (28/31) were common in these 2 pulmonary diseases.The upper lobes were more frequently involved in MAC（10/16） than in Mycobacterium abscessus pulmonary disease（2/15）（P<0.01）. The cavity pattern were more frequently observed in MAC（11/16） and nodular bronchiectatic pattern was found more in Mycobacterium abscessus pulmonary disease（11/15）（P<0.05）.Air space consolidation, cavity and centrilobular nodules or“tree in bud” distributed more lung zones in MAC（55/96，33/96，68/96, respectively） than in Mycobacterium abscessus pulmonary disease（26/90，18/90，48/90, respectively）（P<0.01,P<0.01,P<0.05）. Consolidation was more common in the middle of the right lung (11/16，P<0.05) and the left lung ligule (12/16, P<0.05) in MAC pulmonary disease than in Mycobacterium abscessus pulmonary disease（4/15）.   Conclusion The CT imaging findings of MAC pulmonary disease and Mycobacterium abscessus pulmonary disease have certain similarities, but have different features. It helps for early diagnosis and treatment in clinical practice.

Key words: Mycobacterium avium-intracellulare infection, Mycobacterium infactions, nontuberculous, Tomography, X-ray computed