Pulmonary arterial hypertension (PAH) is a rare disease with a high mortality and complex pathomechanism. Recent studies suggest an important role of genetic factors in the development of PAH. It was shown that patients with BMPR2 mutations present with disease at an earlier age and have more severe haemodynamic disturbances at the time of diagnosis. Interestingly, in this disorder, lifelong pen etrance is estimated to be only about 20% and the mechanism of this phenomenon remains unknown. More recent studies have focused on mutational analyses of genes involved in the transforming growth factor‑beta signalling pathway in this group of patients. Results of these studies are very promising, however, they still need to be confirmed. Moreover, data on the impact of identified mutations on the clinical course, PAH‑specific treatment, and prognosis is required. A multi‑center study is planned in Poland to include patients from referral centers for pulmonary hypertension with diagnosed idiopathic, hereditary and drug‑induced PAH, PAH developing after surgi cal correction of a congenital heart defect, or of pulmonary veno‑occlusive disease and pulmonary capillary hemangiomatosis. The aim of the study is to perform an extended molecular analysis to better understand the molecular basis of PAH pathogenesis, incomplete penetrance, and to create an algorithm for the molecular diagnosis of PAH patients. In addition, the correlation of molecular and clinical data with the effects of specific treatment and prognosis in PAH will be assessed.