Backgroud: Chronic bronchitis is an important phenotype in chronic obstructive pulmonary disease (COPD). The purpose of this study is to evaluate the impact of chronic bronchitis on COPD acute exacerbation (AE). We further aimed to examine the difference in the frequency of AE according to DLCO level. Methods: Patients were recruited from 35 centres in Korea, as part of the COPD cohort (KOCOSS) study. Frequency of AE was compared according to the phenotype. Results: Total 291 patients with COPD were eligible for analysis. Age was 69.8±7.7 (Mean±SD) and 91.1% were male. FVC, FEV1, and FEV1/FVC were 3.3±0.7 L (83.3±13.9%), 1.6±0.5 L (58.8±14.3%), and 48.0±10.3%. Among analyzed patients, 90 (30.9%) patients were compatible with chronic bronchitis phenotype. Patients with chronic bronchitis showed significant higher BMI (23.6 vs 22.7, chronic bronchitis vs non-chronic bronchitis), higher mMRC (1.8 vs 1.4), and higher CAT score (17.5 vs 13.0). During 6 months, AE occurred in 23.3% of chronic bronchitis patients while only 10.2% of non-chronic bronchitis patients experienced AE (P＜0.05). Subgrop analysis according to the level of DLCO was performed. Among patients with chronic bronchitis, AE occurred more frequently in patients with low DLCO. Conclusion: Patients with chronic bronchitis experience AE more frequently than non-chronic bronchitis. Chronic bronchitis combined with low DLCO is high risk for AE.Backgroud: Chronic bronchitis is an important phenotype in chronic obstructive pulmonary disease (COPD). The purpose of this study is to evaluate the impact of chronic bronchitis on COPD acute exacerbation (AE). We further aimed to examine the difference in the frequency of AE according to DLCO level. Methods: Patients were recruited from 35 centres in Korea, as part of the COPD cohort (KOCOSS) study. Frequency of AE was compared according to the phenotype. Results: Total 291 patients with COPD were eligible for analysis. Age was 69.8±7.7 (Mean±SD) and 91.1% were male. FVC, FEV1, and FEV1/FVC were 3.3±0.7 L (83.3±13.9%), 1.6±0.5 L (58.8±14.3%), and 48.0±10.3%. Among analyzed patients, 90 (30.9%) patients were compatible with chronic bronchitis phenotype. Patients with chronic bronchitis showed significant higher BMI (23.6 vs 22.7, chronic bronchitis vs non-chronic bronchitis), higher mMRC (1.8 vs 1.4), and higher CAT score (17.5 vs 13.0). During 6 months, AE occurred in 23.3% of chronic bronchitis patients while only 10.2% of non-chronic bronchitis patients experienced AE (P＜0.05). Subgrop analysis according to the level of DLCO was performed. Among patients with chronic bronchitis, AE occurred more frequently in patients with low DLCO. Conclusion: Patients with chronic bronchitis experience AE more frequently than non-chronic bronchitis. Chronic bronchitis combined with low DLCO is high risk for AE.