remature ventricular contractions (PVCs) lead to irregular heart rhythm and decreasing of left ventricular ejection fraction (LVEF), which may be accompanied with undesirable hemodynamic effects and the development of LV dysfunction. Purpose. The aim of the study is to estimate effects of PVCs on echocardiographic (EchoCG) parameters in children without structural and inflammatory heart diseases.Material and methods. 32 children aged 11.6 ± 5.1 years with idiopathic PVCs (13.4 ± 9.8% per day) were examined. Standard echocardiographic parameters were assessed on normal contraction (NC) of the heart, on extrasystolic contraction (EC) and on the first post-extrasystolic contraction (PEC).Results: Left ventricular end-diastolic diameter (LVEDD) decreased in 71.9% of children and left ventricular end-systolic diameter LVESD increased in 62.5% of children on the EC, which determined decreasing LVEF and LV stroke volume (LVSV) among most of children (96.8%). LVEDD decreased in 62.5% of children and LVESD decreased in 65.6% of children, LVEF increased in 81.3% of children on the PEC, while values of LVSV were less in half of children (46.9%) than the initial parameters, including all children with left ventricular PVCs.Values of LVEF were higher than the initial parameters in the other half of the children (53.1%).LV ejection fraction in children with epicardial localization PVCs was lower than in children with endocardial localization during the EC (53.8 ± 6.7% versus 62.0 ± 10.7%; p = 0.01), which was also noted on PEC (69.8 ± 7.5% on average 75.6 ± 7.0%; p = 0.05). Conclusion.PVCs lead to decreasing of LVEF in children by reducing of LVEDD and by increasing of LVESD. LVEF increased in most children during of postectopic LV contraction, but LV stroke volume did not exceed initial values in children with left ventricular PVCs. LVEF of patients with epicardial PVCs was significantly less than in children with endocardial PVCs on extrasystolic and post-extrasystolic contractions.