ObjectiveAllogeneic hematopoietic stem cell transplantation (allo-HSCT) represents the only curative treatment option for several hematological neoplasms. This study aimed to assess the parameters of body composition as predictors of posttransplant overall survival (OS) and adverse events in patients with leukemia, myelodysplastic syndromes (MDS), and myeloproliferative neoplasms (MPN). MethodsThis was a retrospective study of 122 adult patients who underwent their first allo-HSCT. The CT-based semi-automated measurement of subcutaneous adipose tissue (SAT), visceral adipose tissue (VAT), visceral-to-subcutaneous fat ratio (VSR), sarcopenia in terms of skeletal muscle index (SMI), and myosteatosis based on the skeletal muscle radiation attenuation (SM-RA) was performed. Cox regression analysis was used to assess the association of body composition parameters with OS. ResultsIn the univariate analysis, low SAT and myosteatosis were associated with lower OS (hazard ratio [HR] 2.02, 95% confidence interval [CI] 1.16–3.51, p = 0.01) and (HR 2.50, 95% CI 1.48 – 4.25, p=< 0.001), respectively. This association remained significant after adjusting for relevant covariates, with HR 2.32, 95% CI 1.23 – 4.38, p=0.01 and HR 2.86, 95% CI 1.51 – 5.43, p=< 0.001, respectively. On the contrary, VAT, VSR, sarcopenia, and sarcopenic obesity were not statistically significant in OS. Severe post-transplant adverse events were more common in the low SAT group (odds ratio [OR] 3.12, 95% CI 1.32– 7.40, p=0.01) and OR 3.17, 95% CI 1.31 – 7.70, p=< 0.01 in the age- and sex-adjusted analysis. ConclusionLow SAT and myosteatosis may contribute to an increased risk of mortality, while low SAT appears to increase the risk of severe post-transplant adverse events.