Twenty years after Chernobyl Nuclear Power Plant (NPP) explosion, several million people (by various estimates, from 5 to 8 million) still reside in areas that will remain highly contaminated by its radioactive pollution for many years to come, since the half-life of the major radioactive element released is a little over 30 years. So, new researches should be made to investigate the influence of Chernobyl accident-related pollution on persons living on the contaminated territories. The aim of this study was to examine functional activity of hematopoietic progenitor cells of persons living on the radiation-polluted territories suffering from Chronic Myeloid Leukaemia (CML). The bone marrow of patients with different phases of CML was examined. Immobilised mononuclear cells were cultivated by applying two cultivation models: in vitro and in vivo. Our data suggested that there is no significant difference between results obtained from both cultivation systems used, and the numbers achieved are comparable and can be used to develop the unique scheme of hematopoiesis in health or disease. Functional activity of Hematopoietic Progenitor cells (HPCs) of persons with CML living on the territories polluted after explosion on Chernobyl NPP is significantly higher in comparison with control data. The shift in bone marrow cell’s count to increased quantity of blast and granulocytic progenitor cells was observed after morphological analysis. The data obtained can be suggested as a confirmation of monoclonal nature of CML.