To demonstrate that comorbidity is a mortality prognostic factor in elderly patients with community-acquired pneumonia. PATIENTS AND METHODS: It was a retrospective cohort study. We’d included the medical records of elderly patients hospitalized for communityacquired pneumonia in Internal and Respiratory Medicine services from Belen Hospital during the period January 2007 to December 2012. The sample was 98 patients for each cohort. One cohort was constituted by patients with Charlson Comorbidity Index ≥ 2 and the other one with Charlson Comorbidity Index < 2. The endpoint was in-hospital mortality. We applied chi-square; determine relative risk and the 95% - confidence intervals. RESULTS: General mortality was 17.85%. It was significative greatest in the exposed cohort (25.5% vs. 10.2%; p < 0.05). Hospital length of stay was significative greatest in the exposed cohort (p < 0.05). T...