PURPOSE: To compare the CT findings of mycobacterial infection other than tuberculosis (MOTT) with those of tuberculosis (TB). MATERIALS AND METHODS: The chest CT scans of 30 immunocompetent patients with culture-proven pulmonary MOTT (M:F=11:19; mean age, 51.2 yrs.) and of 24 patients with active tuberculosis (M:F=12:12; mean age, 42.5 yrs.) were analyzed by two radiologists; decisions were reached by consensus. RESULTS: Common findings for both MOTT and TB included bronchogenicaly-spread bronchogenic spread nodular lesion (93.3% for MOTT, 100 % for TB), bronchiectasis (90%, 83.3%), bronchial wall thickening (66.7%, 54.2%), granuloma (63.3%, 75%), parenchymal scarring (53.3%, 54.2), and mediastinal lym-phadenopathy (50%, 37.5 %). Less commonly observed findings were emphysema (46.7%, 29.7%), atelectasis (36.7%, 29.2%), narrowing of a major airway (23.3%, 25%), consolidation (23.3 %, 29.2 %), and pleural disease (16.7%, 29.2%). Except for cavity (30%, 53.3%; p< .05), the frequencies of each finding were not right middle lobe (40%, 16.7%), right lower lobe (63.3%, 33.3%) and lingula division (53.3 %, 25%) was sig-nificantly more common in MOTT than in TB (p < .05). The number of lobes in which bronchiectasis and bronchial wall thickening were involved was greater in MOTT(3.20) than in TB(2.04) (p=.011). CONCLUSION: Although the CT findings of MOTT and TB overlap considerably, cavities are more common in TB, while in MOTT, bronchiectasis in the lower lung zone is more common and bronchiectasis tends to be more extensive.