Assessment of cardiac function is the leading parameter when evaluating the state of the cardiovascular system of patients undergoing chronic hemodialysis. The aim of the paper: to assess the state of the cardiovascular system of these patients using new sensitive echocardiography and Doppler techniques and thus advance the prevention of cardiovascular disease. Method: Twenty children with end-stage renal insufficiency on chronic hemodialysis and twenty healthy controls underwent echocardiographic monitoring using standard Doppler and tissue Doppler imaging. Structural and functional changes in the left ventricle were evaluated. Results: Patients on hemodialysis had significantly greater left ventricular mass indices compared to the controls (p < 0.001). The patients on hemodialysis had preserved systolic function—their fractional shortening, ejection fraction and Sm (systolic myocardial velocity) did not differ significantly compared to the controls (p > 0.05). Early diastolic function in children on hemodialysis was also preserved: the E/A and Em/Am ratio did not differ significantly from the control group (p > 0.05). Children on hemodialysis exhibited impaired late diastolic function (compliance index), that is, considerably higher E/Em compared to controls (p < 0.00). Myocardial Performance Index values showed statistically significant elevation in children on hemodialysis compared to the control group (p < 0.001). Conclusion: Tissue Doppler in tandem with conventional Pulsed Doppler can provide additional information on left ventricular filling pressures (E/Em) in children on hemodialysis. It is therefore recommended to perform routine measuring of Em waves and the E/Em ratio, not only in order to evaluate myocardial relaxation and ventricular filling pressures, but primarily to stratify risk and provide a prognosis.