The aim of this study was to determine the signifi­cance of factors such as transthyretin levels, right diaphragm thickening fraction, amplitude of left diaphragm dome movements, stroke volume index (SVI), cardiac in­dex (CI), SpO2/FiO2 ratio and transthyretin/C-reactive protein in unsuccessful weaning from AV in children with various forms of ARF at the stage of weaning from mechanical ventilation (MV). Materials and methods. We complete the prospective single-center cohort study and enrol 67 patients 1 month - 18 years old with hypoxemic and hypercapnic-hypoxemic acute respiratory failure (ARF). 46 of them need invasive mechanical ventilation (MV) for more than 3 days. We divide them into 1 st group (n=35, they were successfully weaned) and 2 nd group (n=11, they need reintubation and MV within the next 48 hours). We performed ultrasound examination of diaphragm, prolonged non-invasive monitoring of hemodynamic parameters to determine SVI, CI, SpO 2 with esCCO technology (estimated continuous cardiac output), NIHON COHDEN; determination of transthyretin (TTR) with G-Biosciences/Geno Technology, (USA) kit. Data were recorded on the first day of MV (d1), on 3rd, 5th, 7th day of treatment (d 3 , d 5 , d 7 ). Logistic regression method was used to make a predictive model of the probability of unsuccessful weaning from MV. Results. We have established (formula 1), that the risk of unsuccessful weaning from MV in patients with hypoxemic ARF increases with low values of transthyretin serum level, right hemidiaphragm thickening fraction, SVI and high CI. R= -12,008 + 0,242*(TTR, ng/ml) + 1,720*(right hemidiaphragm thickening fraction, %) + 1,711*(SVI, ml/beat/m 2 ) – 3,120*(СІ, l/min/m 2 ) (1). The risk of unsuccessful weaning from MV in patients with hypercapnic-hypoxemic ARF (formula 2) increases with low values of transthyretin serum level, amplitude of left hemidiaphragm movement, SVI, SpO 2 /FiO 2 and transthyretin/C-reactive protein ratio. R= - 42,233 + 0,389*(TTR, ng/ml) + 22,189*(amplitude of left hemidiaphragm movement, mm) + 1,120*(SpO 2 /FiO 2 ) + 2,885*( SVI, ml/beat/m 2 ) + 14,944*(TTR/CRP) (2). Conclusions. The level of transthyretin and SVI in addition to the indicators of thickening fraction of right hemidiaphragm and CI in children with hypoxemic ARF and the amplitude of left hemidiaphragm movements, ratios SpO 2 /FiO 2 and transthyretin/C-reactive protein in children with hypercapnic-hypoxemic ARF might affect the process of weaning from MV. Thus, acute malnutrition with diaphragmatic dysfunction and hyperdynamic type of blood circulation reduce the likelihood of successful weaning from MV and worsen clinical outcome in children with different types of ARF