Background: Nodular bronchiectatic (NB) form of nontuberculous mycobacterial lung disease (NTM) is known to usually involve right middle lobe (RML) and left upper lobe lingular segment. However, the reason of this predilection has not been acknowledged. The primary goal of this study is to evaluate whether there are anatomical risk factors of NB-NTM lung disease. Methods: Fifty patients with NB-NTM lung disease who had both positive NTM culture and NB lesions at RML or lingular segment on computed tomogram (CT) and 100 controls matched by sex, age, height and body weight who showed normal chest CT were randomly selected. Using reconstructed curved multiplanar reformation (MPR) image, lengths, diameters, and angles of RML and lingular bronchi were measured. Results: Of 150 subjects, 64% were female and the median age was 56 years. The angles of bronchi were significantly more obtuse in cases than those of controls both in RML (cases: 46.75±8.87o vs. controls: 51.73±7.76o, p=0.001) and lingular segments (cases: 26.94±8.16o vs. controls: 34.65±9.75o, p＜0.001). In addition, the angles of bronchi of involved segments were also more obtuse than those of non-involved segments both in RML and lingular segments. There were no differences in the lengths and the diameters of bronchi between groups. Conclusions: An obtuse bronchial angle could be an anatomical risk factor of the nodular bronchiectatic NTM lung disease.