Introduction: The treatment with anthracyclines for hematologic malignancies is often associated with early or late phenomenon of cardio toxicity that can be severe and even worse disease prognosis, requiring early diagnosis and specific treatment. Objective: The study of the most important echocardiographic parameters useful for early diagnosis and monitoring of cardiac involvement secondary anthracycline induced cardio toxicity in children with hematological malignant diseases Methods: Patients: 124 patients (aged 3 month – 19 years) treated with anthracyclines for malignant diseases. Doppler echocardiography (echo) evaluated the most important LV systolic and diastolic function parameters. The interval between examinations has been established depending on the cumulative anthracyclines doses (200, 300, 400 > 500 mg/m2). The data were correlated with the dispersion of QT/QTc intervals in 40 patients. Control group: 40 healthy children without cardiovascular suffering. Results: Echo exam revealed suggestive modifications for cardio toxicity in 63 cases (51%) with or without clinical manifestations of cardiac suffering up to heart failure. The most important modifications were found at a cumulative dose >350 mg/m2 : *systolic dysfunction of LV: decrease of ejection fraction (19%);* higher incidence (48%) and precocious onset of the diastolic dysfunction of the LV: relaxation impairment – ratio E/A <1 (17%) or compliance impairment – ratio E/A >2,5 (31%); increase of the deceleration time of E wave – DTE (35%) and of the isovolumic relaxation time – IVRT(28%).The Tei index: increased in 30 cases. ECG: an increase in the dispersion of interval QT/QTc in 73% of patients correlated with the cumulative doses of the anthracyclines >400 mg/ m2 . Conclusions: Diastolic dysfunction of LV occurs earlier and with a superior incidence (48%) versus systolic dysfunction (19%) of LV, proved by decline of the ejection fraction of LV. Diastolic function echo parameters (E, E/A, DT, IVRT) and Tei index allow a precocious detection of antharcyclines – induced cardiotoxicity that are frequently missed or not suspected clinically, especially when the LVEF is normal. The echocardiographic modifications and increased of QT/QTc intervals, well correlated with cumulative doses of the anthracyclines, can highlight the signs of cardiac suffering in the stage infraclinic and it is necessary to be follow up both during and aft er the cytostatic treatment.