The mortality rate of chronic obstructive pulmonary disease (COPD) patients with community-acquired pneumonia (CAP) is reported to be low. However, studies carried out to date have included <20% of critically ill patients. The current authors performed a secondary analysis of a prospective study evaluating 428 immunocompetent patients admitted to the intensive care unit (ICU) for severe CAP. In total, 176 COPD patients were compared with 252 non-COPD patients. In COPD patients, ICU mortality (odds ratio (OR) 1.58; 95% confidence interval (CI) 1.01-1.43) and mechanical ventilation (OR 2.78; 95% CI 1.63-4.74) rates were higher than in non-COPD patients. The ICU mortality was 39% for COPD patients initially intubated and 50% for those who failed noninvasive ventilation. The proportion of patients who were males, aged >/=70 yrs, smokers and who had chronic heart disease or Pseudomonas aeruginosa were higher in COPD patients. Inappropriate empirical antibiotic therapy was associated with higher mortality (OR 3.8; 95% CI 1.19-12.6). ICU mortality in COPD patients with adequate therapy was associated with bilateral pneumonia (OR 2.32; 95% CI 1.18-4.53) and shock (OR 3.53; 95% CI 1.31-9.71). In conclusion, chronic obstructive pulmonary disease patients hospitalised with community-acquired pneumonia in the intensive care unit had higher mortality and need of mechanical ventilation when compared with patients without chronic obstructive pulmonary disease.