Unlike previous research, which reported the prevalence of chronic bronchitis to be 5%, our study reported the prevalence of COPD to be as high as 26.4%. In a previous report, the overall prevalence of COPD in Koreans older than 40 years was 13.4% and increased to 19.4% in men. In our analysis, 12.2% of the total study population had COPD. Focusing on patients with chronic cough, the prevalence of COPD increased to 26.4%. Therefore, physicians should not underestimate the possibility of COPD in patients with chronic cough.