OBJECTIVES: It is well known that the patients treated with fixed combination of inhaled corticosteroid/long acting beta-2 agonist(ICS/LABA) shows pneumonia as an adverse event. The purpose of this study is to compare the risk of hospitalization by pneumonia between two different ICS/LABA substances. METHODS: Retrospective cohort study was conducted using 2013 HIRA-NPS(National Patients Sample of Health Insurance Review and Assessment Service) database of Korea. The cohort consisted of the patients who were prescribed DPI(Dried Powder Inhaler) form of fluticasone/salmeterol and budesonide/formoterol at least once as an initial user from Feb 2013 to Dec 2013. The patients who were enrolled to the cohort was observed until the first hospitalization due to pneumonia(J12-18 of ICD-10 code) occurrence. The incidence rate of pneumonia were estimated and crude and adjusted hazard ratio of pneumonia associated with ICS/LABA use with 95% confidence intervals were estimated by Cox proportional hazard model. RESULTS: The cohort included 5,939 patients of which 4,531 patients(76.3%) treated with fluticasone/salmeterol and 1,408 patients(23.7%) treated with budesonide/formoterol. The pneumonia incidence rate was higher with fluticasone/salmeterol which was 8.50 per 100 person-year while the pneumonia incidence rate of budesonide/formoterol was 5.14 per 100 person-year. Compared with budesonide/formoterol, the pneumonia risk was higher in patients treated with fluticasone/salmeterol(hazard ratio: 1.48, 95% CI: 1.06-2.06). The results were similar in sensitivity analysis which regulated definition of initial users. CONCLUSIONS: The higher risk of pneumonia occurrence was observed for fluticasone/salmeterol which shows the intra-class difference of fixed combination of inhaled corticosteroid/long acting beta-2 agonist. The difference between the adverse event occurrences should be considered before selection of drugs for the patients.