The conducted research was aimed at examining the relationship between changes in the concentration of pro-angiogenic cytokines between the group of patients and the control group in glioma and acute lymphoblastic leukemia, determining the strength and direction of interactions between the determined cytokines depending on the disease and determining the diagnostic usefulness of the VEGF-A, VEGF-R2, and FGF-2 determination methods for glioma and VEGF-A and FGF-2 for leukemia. The gene discussed is KDR; the disease is central nervous system cancer.