Background. Damage markers of blood-air barrier are important for studding pathological process in lungs in children with acute lymphoblastic leukemia (ALL). Purpose is to analyses pulmonary complications and to assess IL-6 and TGF-β levels in the exhaled breath condensate (EBC) in children with ALL and its prognostic value. Materials and Methods. 40 children with ALL aged 6–17 years were examined. 1st group included newly diagnosed ALL (n = 18). 2nd group involved ALL survivors who had completed course of ALL IC BFM 2009 protocols (n = 22). The control group consisted of 15 healthy children. The levels of IL-6 and TGF- β in the EBC were analyzed by ELISA. Results and discussion. Pulmonary complications presented in 82.5% of children with ALL during chemotherapy and in 15.8% of ALL survivors. IL-6 and TGF-β levels in EBC were significantly higher in both ALL groups than control: IL-6 p1-C = 0,000001; p2-C = 0,000000; TGF-β p1-C = 0.000014; p2-C = 0.009364. 1st group had higher levels of IL-6 and TGF-β in the EBC than 2nd group: IL-6 p1-2 = 0,000000; TGF-β p1-2 = 0.000141. There was a positive correlation between IL-6 and TGF-β levels (r = 0.681176, p = 0.000001). According to ROC analysis, IL-6 level in EBC collected during Protocol 1 > 47.64 pg/ml can be prognostic for pulmonary complications during chemotherapy (AUC 0.875; Sensitivity 75.0%; Specificity 100,0%). Level of IL-6 > 49.96 pg/ml can predict pneumonia during chemotherapy (AUC 0,883; Sensitivity 100.00%; Specificity 81.82%). IL-6 level after the total course of chemotherapy > 23.64 pg/ml can predict pulmonary complications in ALL survivors (AUC 0.819; Sensitivity 75.00%; Specificity 81.82%). TGF-β level in EBC after the completion of chemotherapy > 19.93 pg/ml can be prognostic for pulmonary complications in ALL survivors (AUC 0.896; Sensitivity 100.00%; Specificity 77.78%). Conclusions. IL-6 and TGF-β levels in EBC can be prognostic for pulmonary complications in children with ALL.