Background: Community-acquired pneumonia (CAP) is associated with higher morbidity, mortality and economic burden among adults. The cost of the disease increases according to the site of care (home, ward, ICU) and the length of hospital stay (LOS). The early recognition of prognostic factors for prolongs hospital stay it will be helpful to decrease the cost of CAP. Methods: A prospective observational study of consecutive CAP patients was performed at Sotiria Hospital of Athens-Greece, between June 2011-July 2018. We divided the population in two groups: prolonged length of stay (PLOS) group (hospitalization equal or higher than the mean LOS) and short length of stay (SLOS) group (less than the mean LOS). Results: Of a total 930 patients (55% men, 63.7 years (SD 18) with a mean length of hospital stay of 11 days (SD 9.6), 286 patients has PLOS of 20 days (SD 13). The patients with PLOS were older (66 y vs. 63y, p=0.023) and had received more often antibiotics before admission (53% vs. 44%, p=0.015). They presented with more severe CAP according to PSI score (115 vs. 98, p<0.001). The clinical evolution was more often complicated with systemic complications (43% vs. 19%, p<0.001) and need for ICU (14% vs. 6%, p<0.001) admission, but not with higher mortality. Conclusions: In the multivariate analysis, the severity of CAP (PSI class >4),previous antibiotics, hy-poalbuminemia, therapy with corticosteroids, pulmonary complications and the non-adherence to guidelines are significantly related with prolonged hospitalization for CAP.