Doxorubicin is antitumor antibiotic extensively metabolized in the liver, and liver antioxidant capacity, including that provided by glutathione production. The aim of this study was to investigate whether doxorubicin containing chemotherapy changes metabolic liver function during treatment of childhood acute lymphoblastic leukaemia. Total protein concentration in serum, concentration of total, conjugated and non conjugated bilirubin, activity of aspartat aminotransferase (AST), alanine aminotransferase (ALT), gamma glutamyl transferase (ãGT), lactate dehydrogenase and creatin kinase activity were measured before and after treatment with doxorubicin containing chemotherapy and in the control group. Caffeine was applied as metabolic marker via controlled consummation of Coca-Cola and 8-hour urine was collected immediately afterwards. In the collected samples, urinary thioethers and caffeine metabolites concentrations were measured. Chemotherapeutic regiment established for initial treatment of childhood ALL containing prednisone, vincristine, doxorubicin and L-asparaginase did not alter metabolic liver function. This regiment did not change liver enzyme activity. Applied chemotherapy also did not alter caffeine biotransformation, but it did increase urinary thioethers excretion.