Background/Aims: Chronic obstructive pulmonary disease (COPD) is a major cause of mortality in the world. There are no population-based studies on long-term mortality in COPD patients in Korea. Methods: Using the large, population-based, National Health Insurance Service-National Sample Cohort (NHIS-NSC), we identified COPD patients using the International Classification of Disease-Tenth Revision (ICD-10) and prescription details in the NHIS-NSC during 2003 to 2013. We analyzed the survival curves of COPD patients by sex, age, and cause of death. Results: A total of 14,127 individuals older than 40 years were diagnosed with COPD. There were a total of 3,695 deaths (26.2%) in COPD patients during the study period. The 5-year mortality of COPD patients was 25.4% (29.9% in males and 19.1% in females). The mortality rate increased rapidly with age. The most common cause of death in COPD was chronic lower respiratory disease. Conclusions: This study described long-term mortality in COPD patients in Korea. Higher mortality was observed in males, and it was closely related to age.