Aim. To assess the body composition and functional activity (FA) parameters in men with heart failure (HF) of various nature depending on the stage, class and echocardiographic characteristics of the disease.Material and methods. The study included 100 men aged 23-70 years. The main group consisted of 60 men with HF, the control group — 40 men without HF. Quantitative body composition assessment (fat, lean and bone body mass) was carried out using dual-energy X-ray absorptiometry (DXA). Physical activity was assessed using handgrip test, short physical performance battery (SPPB) test, 6-minute walk test (6MWT), and Timed Up and Go (TUG) test.Results. In the HF group, there were a significant decrease in total bone mass, trunk and limb bone mass, total muscle mass, trunk and limbs’ muscle mass, appendicular skeletal muscle index (ASMI), and FA as HF class increased. Fat mass did not differ in individuals with different HF class and stage. HF class was an independent factor in the reduction of total bone mass (b=-301,9, p=0,015), total muscle mass (b=-1903, p=0,03), limb bone mass (b=-147,6, p=0,013) and appendicular muscle mass (AMM) (b=-1903, p=0,001). Total bone mass (b=-2,637, p=0,02) and AMM (b=-3,512, p=0,01) were independently associated with the Vasilenko-Strazhesko HF stage. AMM also had an independent association with left ventricular ejection fraction (LVEF) (b=0,274, p=0,03). The average body composition scores did not differ between the study and control groups, while the scores of handgrip test, 6MWT, SPPB and TUG test were significantly worse in the HF group. NYHA HF class, stage of HF, LVEF, left ventricular end-diastolic volume (LVEDV) and pulmonary artery systolic pressure (PASP) made an independent contribution to FA decrease in men with HF.Conclusion. In patients with HF, there was deterioration in musculoskeletal parameters depending on HF class, stage and LVEF, without significant differences compared to the control group. There was no association of fat mass with the disease, clinical and echocardiographic characteristics. The average parameters of muscle strength and tests of FA were reduced in men with HF compared with the control group and depended on the NYHA class and stage of HF, LVEF, LVEDV, and PASP.