Introduction of novel diagnostic methods and multimodal therapy has resulted in about 70% probability of cure of childhood neoplasms. However, treatment results of some neoplastic diseases in children, including chronic myelogenous leukemia (CML) still remain unsatisfactory. The only chance of cure remains allogeneic hematopoietic stem cell transplantation, however availability of transplantation is still low as a limited number of donors is available. In neoplastic diseases in which treatment results remain poor, intensification of treatment components (chemotherapy, radiotherapy) did not succeed in improving the treatment results. In recent years no improvement was made in gene therapy. With introduction of new drugs that selectively inhibit mechanisms of maturation and proliferation of cancer cells, new hope has arisen. In our paper we present the mechanism of action of imatinib, the tyrosine kinase inhibitor which was employed in the treatment of CML and gastrointestinal stromal tumors. Currently, there are several ongoing studies assessing the efficacy of this novel drug in the therapy of brain tumors, neuroblastoma, lung and prostate cancer.