Yoonki Hong,1 Wonjun Ji,2 Soojeong An,3 Seon-Sook Han,1 Seung-Joon Lee,1 Woo Jin Kim1 1Department of Internal Medicine, Environmental Health Center, Kangwon National University Hospital, Chuncheon, South Korea, 2Department of Pulmonary and Critical Care Medicine, Asan Medical Center, University of Ulsan College of Medicine, Seoul, South Korea, 3Department of Statistics, Kangwon National University, Chuncheon, South Korea Background: There is growing evidence about sex-related phenotypes of COPD. However, the sex differences in COPD mainly result from smokers. This study evaluated the sex differences in nonsmoking patients with COPD, focusing on structural changes in the lungs in airway diseases and emphysema. Methods: Ninety-seven nonsmoking patients, defined as having