The aims of this study were to evaluate clinical course of community-acquired pneumonia (CAP) in patients with chronic heart failure (CHF) and to assess the time course of serum biomarkers, such as C-reactive protein (CRP), procalcitonin (PCT), interleukin-6 (IL-6), tumor necrosis factor α (TNF-α), and brain natriuretic peptide (BNP), at baseline and after treatment in patients with CAP and CHF. Methods. This was a prospective observational study. Adult patients with CHF admitted to a hospital due to suspected CAP were recruited in the study. The diagnosis of CAP was confirmed by chest computed tomography (CT). Subsequently, patients were assigned to the group 1 (with confirmed CAP) or the group 2 (with respiratory infections other than CAP). Echocardiography was performed in all patients at baseline and in follow-up visits. In addition to the routine clinical examination and laboratory tests, serum biomarkers were measured in all patients at admission (Visit 1), at days 10 to 14 (Visit 2), and at days 28 to 42 (Visit 3). Standard statistical methods were used for data analysis. Results. Seventy patients who met the inclusion criteria were enrolled in this study; of them, 35 patients had confirmed CAP and 35 patients had respiratory infections other than CAP. Both groups were similar for demographic and clinical characteristics, as well as for laboratory, echocardiographic and radiological findings. CAP did not affect the clinical course of CHF and echocardiographic parameters did not differ significantly between the groups. Clinical signs of both diseases improved after the treatment in majority of patients. Echocardiographic parameters also improved in both groups that indicates the improvement in cardiac dysfunction under the treatment. During the follow-up, the most prominent changes were seen in CRP level which was significantly higher at baseline in CAP patients compared to patients with other respiratory infections. CRP level decreased at Visit 2 in both groups and in Visit 3 in CAP group. CRP levels differed significantly between the groups both at Visits 1 and 2. Other biomarkers, such as PCT, IL-6, and BNP, were significantly higher at Visit 1 compares to Visit 2. TNF-α level did not change significantly neither in any group during the study nor between the groups at any study time. Conclusion. CAP did not affect the clinical course of CHF. Inflammatory biomarkers, such as CRP, PCT, and IL-6, could be used additionally to the routine diagnostic procedures to differentiate between CAP and other respiratory infections in patients with CHF. CRP is the most promising biomarker. Serum levels of the biomarkers decreased significantly under the standard hospital treatment of CAP and CHF; this could be considered to evaluate treatment success and prognosis. © 2019 Medical Education. All rights reserved.