Background. Wilms' tumor is the most common kidney cancer in children. Treatment consists of pre-and post-operative chemotherapy, surgery and in some cases radiotherapy. The treatment of nephroblastomas is very effective. Hence, the population of adult patients cured of this cancer in their childhood is steadily growing, generating a need for longterm health assessment, including renal function, due to the specifications of the therapy and the location of the tumor. Objectives. The aim of the study was to evaluate nephrological complications after treatment for nephroblastoma. Material and Methods. The study group consisted of 50 children treated in the Department of Pediatric Hematology, Oncology and Bone Marrow Transplantation at Wroclaw Medical University (Poland) from 2002 to 2012. An analysis of the patients' medical histories was carried out. The glomerular filtration rate estimated by the Schwartz formula (GFR by Schwartz), serum creatinine levels, urea and electrolyte concentrations; the results of urinalysis and blood pressure were assessed. Each of these analyses was performed at the time of diagnosis, at the end of therapy, as well as 6 months, one year and two years after its completion. Results. The study showed that, in most cases, implemented therapy had no significant impact on the deterioration of renal parameters in the two-year period following treatment for Wilms' tumor. However, the group of patients treated with cyclophosphamide and carboplatin required more careful monitoring, due to a higher risk of renal function deterioration. Conclusions. The study shows that the problem of nephrotoxicity after treatment for Wilms' tumor is more frequent than indicated in other studies; however, the deterioration of kidney function in most cases is not serious. Additional attention should be paid to patients treated with cyclophosphamide and carboplatin. Assessment of the early and late effects of the treatment is a key element in improving the quality of the patients' life (Adv Clin Exp Med 2015, 24, 3, 497-504).