The aim of the study was in comparative analysis of the results obtained using the cardiac catheterization and the echocardiographic parameters in patients with atrial septal defect of the ostium secundum type. The studies have been performed in the group of 31 patients aged 16 to 58 years (mean = 31.9) in whom the right heart catheterization of the two-dimensional or Doppler's echocardiography has been performed. The following parameters have been analysed: pulmonary flow (Qp), systemic flow (Qs), shunt size (S), the Qp/Qs ratio, the systolic gradient via tricuspidal valve (TPG). The highest correlation in the invasive and the not invasive examination has been shown for TPG (r = 0.93). Other parameters showed no statistically significant differences.