OBJECTIVE The study objective was to assess plasma N-terminal-pro-brain natriuretic peptide (BNP) levels and to evaluate left ventricular mass as well as left ventricular systolic and diastolic functions in 44 children who had undergone treatment for acute lymphoblastic leukaemia and Hodgkin's lymphoma, with regard to gender, age at disease onset, time that had passed since therapy completion, cumulative dose of antracyclines and mediastinal radiotherapy applied. METHODS The median levels of pro-BNP were found to be higher in the whole study group as compared with the control (55.9 ± 53.1 ng/mL vs. 38.5 ± 47.7 ng/mL, P= 0.059). The pro-BNP values >80.0 ng/mL (standard deviation score (SDS)) were noted in 11/44 patients, including those exceeding 115.0 ng/mL (2 SDS) - in 6/44 patients. RESULTS No correlation was observed of pro-BNP levels with the accumulated dose of antracyclines (r=-0.42, P= 0.79) or mediastinal radiotherapy (r= 0.197, P= 0.2). However, negative correlation was found between pro-BNP and the time that had passed since therapy completion (r=-0.378, P= 0.009). In echocardiography, shortening and ejection fractions remained normal, whereas the indexed stroke volume was below 40 mL/m(2) in 16/44 patients. The E/A index below 1.5 was found in 6/44 cases. The left ventricular systolic mass remained within the normal range. Negative correlation was noted between isovolumetric diastolic time and pro-BNP level. CONCLUSIONS Increased levels of pro-BNP after anti-cancer treatment with the involvement of cardiotoxic substances may indicate the first symptoms of myocardial dysfunction, despite the lack of major echocardiographic disorders.