RESULTS: A total of 729 patients hospitalized with COPD exacerbations were included. There were 207 eosinophilic and 294 neutrophilic COPD exacerbations. In blood gas analysis at admission, pH (7.43±0.80 vs. 7.41±0.56, P=0.031) was lower in eosinophilic COPD patients, but the level of carbon dioxide (43.68±15.84 vs. 42.46±8.98, P=0.024) was higher in patients with neutrophilic COPD. There were no significant differences in pulmonary function tests except lower FEV1 (44.55±15.40 vs. 50.13±21.63, P=0.044) in neutrophilic COPD. There were no significant differences in the duration of hospital stay and treatment outcomes including mortality, but the admission rate of intensive care unit was higher in neutrophilic COPD patients (11.6% vs. 1.8%, P=0.018).