Hyperleucocytosis is associated with higher morbidity and mortality related to possible development of leucostasis, tumour lysis syndrome and/or disseminated intravascular coagulation. There is insufficient evidence of the need for leukocytapheresis during early treatment of hyperleucocytosis, and its efficiency remains controversial, although leucoreduction is a measure that can prevent adverse events and death. The aim of this study was to analyse the safety and effectiveness of therapeutic leukocytapheresis and its influence on early mortality in our case series, adjusted to independent mortality risk factors described in the literature.