The purpose of this study was to determine the blood concentration of sST2 and evaluate the correlations between sST2 and the clinical, instrumental, and echocardiographic characteristics of patients with CHFrEF (chronic heart failure with reduced ejection fraction) and CHFpEF (chronic heart failure with preserved ejection fraction), as well as to evaluate the sST2 informativeness in comparison with NT-proBNP. The study involved 160 patients diagnosed with CHF (86 men and 74 women, mean age of 72.4±8.7 years). According to the LVEF value, the patients were divided into two groups: CHFpEF (EF≥50%) was recorded in 69 people, CHFrEF (EF