BACKGROUND We analysed the usefulness of Doppler echocardiography to determine the presence and severity of pulmonary hypertension (PH) in children. METHODS The whole group consisted of 63 patients, 42 with congenital heart disease that underwent cardiac catheterization (32 of whom had PH = study group) and 21 healthy children. These 21 patients and the remaining 10 without PH at cardiac catheterization made up the control group. All children were studied with Doppler Echocardiography to evaluate the pulmonary flow pattern with the sample volume placed in the pulmonary artery trunk, 1 cm distal to the pulmonic valve. The preejection period (PEP), ejection period (EP), acceleration time (AcT), the indexes PEP/EP, PEP/AcT, AcT/EP and the morphologic pattern of the pulmonary flow (type I: with peak flow velocity at midsystole; type II: with peak flow velocity in early systole; type III: with midsystolic notching) were analysed and quantitative parameters corrected according to hear rate by dividing theirs value by the square root of R-R interval. In the hemodynamic study we analysed the systolic (SPAP), diastolic and mean pulmonary artery pressure, and the mean pulmonary pressure/mean systemic pressure ratio (Pp/Sp). We compared the echocardiographic variables in both, study and control groups, and analysed the hemodynamic and echocardiographic correlation between the variables in question. RESULTS Pattern I of pulmonary flow was associated with absence of PH and pattern II and III with PH (p < 0.001). The best results of quantitative variables were either corrected AcT (AccT) rather less in the study group than in control group (2.89 +/- 0.56 vs 4.05 +/- 0.56 ms, p < 0.001) and PPE/AcT index, 1.28 +/- 0.3 in the hypertensive group and 0.78 +/- 0.16 in the control group (p < 0.001). The best correlation were AcT with SPAP (r = -0.82) and Act with Pp/Sp ratio (r = -0.84). CONCLUSIONS We consider that pulmonary flow analysed with Doppler echocardiography is a reliable, suitable and non-invasive method to evaluate PH in children.