Abstract Introduction Despite recent achievement in the diagnosis and treatment of heart failure, the prognosis for disease remains unfavorable especially in elderly patients. It has been recently actively proposed to introduce a comprehensive geriatric assessment to determine the group of adverse outcome and frailty, however the assessment of geriatric syndromes in acute decompensated heart failure (ADHF) among hospitalized patients is poor. Aim To assess the prognostic role of malnutrition and dependence on outside help in hospitalized elderly patients with ADHF. Materials and methods The study included 60 patients over 75 years old who were hospitalized for ADHF. The median [IQR] age was 83.0 [77.0-87.0] years, 41.7% (n=25) were men. The preserved left ventricular ejection fraction (LVEF) prevailed – 51.2% (n=22), moderately reduced and low LVEF – 23.3% (n=10) and 25.6% (n=11), respectively. Total/severe dependence on outside help was determined with Barthel Index of ≤60 points, malnutrition – with a Mini Nutritional Assessment Scale of <17 points, sarcopenia with SARC-F ≥4 points. At discharge, all patients underwent bioimpedance analysis of body composition (BIA). The primary endpoint was hospital mortality. Results 48.3% (n=29) of hospitalized elderly patients with ADHF had total/severe dependence on outside help. This group of patients had a higher risk of malnutrition (OP 2.01, 95% CI 1.49-2.83, p=0.04) and sarcopenia (OP 8.25, 95% CI 1.55-44.02, p=0.01). Elderly patients with ADHF and malnutrition had a more severe functional class (NYHA III-IV) than patients without malnutrition (97.1% vs. 66.7%, respectively, p=0.02). There were no differences in ADHF phenotypes depending on the presence of malnutrition. The ability to self-serve according to Barthel Index has positively correlated with the BIA Index (r=0.483, p=0.04). The risk of sarcopenia on the SARC-F scale has negatively correlated with fat, lean and active cell mass according to BIA (r=-0.538, r=-0.599 and r=-0.532, respectively, p<0.05). Elderly patients with ADHF and a combination of total/severe dependence on outside help and malnutrition (27.9%, n=12) had higher inflammation level (neutrophil-lymphocytic index 5.6 [2.6-7.7] vs. 3.9 [2.0-6.0], p=0.03, respectively) and the need for longer intravenous diuretic therapy (OP 4.38, 95% CI 1.21-15.81, p=0.03) compared with patients without these disorders (72.1%, n=31), The primary endpoint was reached by 4 patients, in 100% of cases there was a combination of total/severe dependence on outside help and malnutrition. Conclusion The combination of total/severe dependence on outside help and malnutrition is an unfavorable prognostic marker of hospital mortality in hospitalized elderly patients with ADHF. A comprehensive geriatric assessment and determination of body composition can identify a risk group for an adverse outcome.