Background: Chronic obstructive pulmonary disease(COPD) has been one of the major diseases and prevalence and mortality is still increasing worldwide. Methods: Korean National Health and Nutrition Examination Survey(KNHANES) is a nationwide cross-sectional survey of the Korean population and 50,405 subjects performed health and nutritional survey during fourth and fifth KNHANES. Among them, 25,812 subjects aged over 40 years old performed spirometry and a trained interviewer administered a questionnaire on respiratory diseases and various health-related information, including educational level, residential pattern, income, smoking, and other risk factors of COPD. The educational level was classified into four groups and household income was stratified into 4 quartiles. The statistical analyses were carried out using SAS 9.3 (SAS Institute Inc.). T-test, Chi-square test and logistic regression analysis were done. Results: Data from 15,971 adults who performed spirometry adequately were used for this analysis. Of all subjects, 6,871 (43.0%) were male and 9,100 (57.0%) were female. The mean age was 56.7 for men and 57.1 for women. Prevalence of COPD, defined as FEV₁/ FVC＜0.7, was 13.6% (22.7% male; 6.7% female). COPD is more prevalent in older age group, male gender, heavy smoker and lower income and educational level population. Multivariate analysis showed that older age, male gender, smoking status, and lower educational level were significant independent risk factors for COPD. The prevalence of smoker is higher and duration of smoking is longer in lower educational level group and total amount of smoking expressed as pack-year is bigger. Conclusions: Low educational level may considered as an independent risk factor of COPD in Korean adult population and further study is needed.