In this study, our aim was to evaluate the laboratory findings of pediatric patients with Polycythemia Vera (PV), and Essential Thrombocythemia (ET). For this, bone marrow and peripheral blood samples were collected from eight patients. Mononuclear cells were isolated and counted, then, to analyze cells, colony Forming Cell (CFC) assay was performed and colonies were counted and identified. We performed 14 CFC assays for eight cases. Colonies grew successfully for three patients and did not grow from the remaining five patients. In conclusion, analysis of cell types by CFC can aid in the confirmation of diagnosis of pediatric Ph-negative MPN even in the absence of known driver mutations.