Abstract: Objective:To determine the predictive factors for treatment responsiveness in patients with chronic obstructive pulmonary disease(COPD) at 1-year follow-up by performing quantitative analyses of CT scans. Methods:The subjects were 113 patients with COPD. Patients received a combination of inhaled long-acting beta-agonists and corticosteroids twice daily for 3 months and subsequently received medications according to the practicing clinician's decision. The emphysema index(EI), airtrapping indices(ATI), and hypothetical airway wtih internal perimeter of 10 mm(Pi10) were obtained with baseline CT scans. Clinically meaningful treatment response was defined as an absolute increase of ≥ 0.225 L in the forced expiratory volume in 1 second(FEV1) at the one-year follow-up. Multivariate logistic regression analysis was performed to investigate the predictors of an increase in FEV1. Results:Treatment response was noted in 23 patients(20.4%). The mean FEV1 increase in responders was(0.35 ±0.11) L. On univariate analysis, the air-trapping index(ATI), ATI of the emphysematous area, and Pi10 parameter differed significantly between treatment responders and non-responders(all P<0.05). Multivariate analysis revealed that the Pi10 was the only independent variable predictive of an FEV1 increase(OR:1.78; 95% CI:1.221~2.618, P=0.003). Conclusion:Pi10, an airway parameter measured by baseline quantitative chest CT, can be used to predict an increase in FEV1 of ≥ 0.225 L in patients with COPD during a 1 year follow-up period.