OBJECTIVES: The aim of this study is to investigate the medical costs of COPD patients in South Korea. METHODS: We enrolled 300 COPD patients who had been treated and followed up for more than one year in the three hospitals from 2012 to 2013. The hospital electronic database was used to obtain medical costs and the medical records were reviewed by physicians (respiratory specialists) to assess clinical characteristics. We calculated annual maintenance costs per-patient according to disease severity, except the costs which were related to COPD exacerbation. The costs of COPD exacerbation per-case was calculated and divided into severe-exacerbation (hospitalization and emergency visit) costs and non-severe-exacerbation (outpatient visit) costs. RESULTS: The annual maintenance costs per-patient was KRW 351,599, KRW 401,068, KRW 573,010 and KRW 999,506 for mild, moderate, severe and very-severe according to GOLD criterion, respectively. In case of the COPD exacerbation, the costs per-case for each non-severe exacerbation and severe-exacerbation was KRW 163,495 and KRW 2,765,086. CONCLUSIONS: The severity of disease and exacerbation of COPD have a substantial impact on the medical costs of COPD patients. Improvement of lung function and reduction of occurrence of COPD exacerbation will be beneficial for the reduction of the healthcare expenditures.