Pharmacogenomics provides knowledge regarding how genetic polymorphisms affect treatment responses. Such an approach is particularly needed in cancer therapy, as most chemotherapeutics drugs affect both tumor and normal cells, are ineffective in many patients and exhibit serious side effects. Leukemia exists in two different forms, myeloid and lymphoid. Acute lymphoblastic leukemia more frequently occurs in children, whereas the risk of acute myeloid leukemia is more common in adults. Despite significant progress in the treatment of these diseases, therapy is still unsuccessful in many patients. Prognosis is particularly poor in adult acute myeloid leukemia. Treatment failure in childhood acute lymphoblastic leukemia due to drug resistance remains the leading cause of cancer-related death in children. Here, we provide an overview of pharmacogenetics studies carried out in children and adults with acute lymphoblastic leukemia and acute myeloid leukemia, attempting to find the associations between treatment responses and polymorphisms in the genes whose products are needed for metabolism, and effects of drugs used in the treatment of leukemia.