The impact of pulmonary hypertension (PHT) on right ventricular and left ventricular (LV) function in children with PHT is unknown, and echocardiographic data combining conventional and Doppler tissue imaging (DTI) on PHT in children are sparse.Forty-one children (18 male; mean age, 7.9 ± 5.6 years) with PHT and structurally normal hearts (27 with idiopathic PHT, 14 with associated PHT) and 44 age-matched healthy controls were assessed using conventional echocardiography and DTI.Children with PHT had enlarged tricuspid valve diameters, right atrial areas, pulmonary artery dimensions, and LV eccentricity indices. In addition, pulmonary acceleration time and tricuspid annular plane systolic excursion were significantly reduced in patients compared with controls. DTI revealed that children with PHT had significantly lower systolic (S) and early diastolic (E) velocities at the tricuspid and septal levels. Despite preserved LV ejection fractions, left lateral free wall systolic velocities were significantly reduced in patients with PHT. Significantly reduced LV rapid filling velocities (E) suggested an underloaded left ventricle or LV diastolic dysfunction in children with PHT compared with controls. Pulmonary acceleration time and tricuspid annular plane systolic excursion correlated best with DTI systolic tricuspid and septal velocities.Despite not being evident on conventional two-dimensional echocardiography, LV systolic performance appears to be impaired in children with PHT. Quantitative DTI assessment of ventricular function and ventricular-ventricular interactions in this setting might provide further insights into the mechanisms leading to end-stage PHT and may guide clinicians to optimize antifailure treatment.