Background: Data comparing the clinical characteristics and outcomes in chronic obstructive pulmonary disease (COPD) patients hospitalized with community-acquired pneumonia (CAP-COPD) and acute exacerbation (AECOPD) are very limited. Methods: Eighty episodes of hospitalization in 65 CAP-COPD patients, and 111 episodes of hospitalization in 82 AE-COPD patients were included in this study. The baseline characteristics, clinical presentations, potential bacterial pathogens and clinical outcomes in these patients were retrospectively reviewed and compared. Results: No significant differences were found between the two groups in parameters related to COPD and co-morbidities, except a higher rate of male among CAP-COPD patients. Clinical presentations by symptoms and laboratory findings on admission were significantly more severe in CAP-COPD patients, who showed higher rates of fever and crepitation, but less wheezing than AE-COPD patients. S. pneumoniae and P. aeruginosae were the most common bacterial pathogens in both groups. With no difference in the overall hospital mortality between both groups, the mean length of hospital stay was significantly longer in the CAP-COPD patients than in AE-COPD patients (15.3 vs. 9.8 days, respectively, p<0.01). Additional analysis on CAP-COPD patients showed that systemic steroid use did not influence the length of hospital stay. Conclusion: Although there was no significant difference in bacterial pathogens and overall hospital mortality between the two groups, CAP-COPD patients had more severe clinical symptoms and laboratory findings at presentation, and longer hospital stay than AE-COPD patients.