Chronic heart failure (CHF) is one of the most common comorbidities in elderly patients with community-acquired pneumonia (CAP). The aim of this study was to investigate etiology of CAP in patients with concomitant CHF. Methods. This prospective observational study involved adult hospitalized patients with CAP and concomitant CHF. CAP was confirmed by chest X-ray. Sputum samples or oropharyngeal swabs, blood and urine samples were collected in all eligible patients before starting the therapy with systemic antibiotics. Sputum was cultured for «typical» bacterial pathogens, such as Streptococcus pneumoniae, Staphylococcus aureus, Enterobacterales, etc., in accordance with standard methods and procedures. Mycoplasma pneumoniae, Chlamydophila pneumoniae and respiratory viruses in sputum or oropharyngeal swabs were identified using the real-time polymerase chain reaction (PCR). Urine samples were used to determine serogroup 1 Legionella pneumophila and S. pneumoniae soluble antigens using bedside immunochromatography. Results. Fifty patients were enrolled in the study. The mean age was 72.2 ± 9.5 years, 27 (54%) were females. The etiology of CAP was identified in 23 cases (46%). S. pneumoniae was the most common pathogen (16/23; 69.7%) followed by respiratory viruses (3/23; 13.1%), such as type 3 parainfluenza virus, coronavirus, human metapneumovirus; Haemophilus influenzae (1/23; 4.3%), S. aureus (1/23; 4.3%), and Klebsiella pneumoniae (1/23; 4.3%). S. pneumoniae and parainfluenza virus co-infection was diagnosed in one of 23 patients (4.3%). Conclusion. S. pneumoniae and respiratory viruses were predominant causative pathogens of CAP in hospitalized adults with concomitant CHF. Therefore, bedside tests for urine pneumococcal antigens should be used more widely considering difficult sputum expectoration in elderly. Atypical bacterial pathogens (M. pneumoniae, C. pneumoniae, L. pneumophila) were not identified in this study, so the routine PCR-test and urine tests for L. pneumophila antigens are thought to be not useful. © 2019 Medical Education. All rights reserved.