Introduction: Pulmonary arterial hypertension (APAH, IPAH) is a devastating, progressive disease with increasingly debilitating symptoms.Increased pulmonary vascular resistance results in extensive heart structural changes, limits patients exercise capacity and, eventually, leads to right heart failure.Current therapies for pulmonary arterial hypertension slow down disease progression but are not curative.Many children eventually fail medical treatment and require transplantation.New approaches to treatment will be the only means to benefit patients.Stem cell research has been a major contraversion for the last decade.Materials and Methods: Possibility for revascularisation of pulmonary arterial blood vessels in patients suffering from severe forms of pulmonary arterial hypertension after intrapulmonary delivered autologous mesenchymal (mononuclear) stem cells have been studied in two (2) patients aged 9 and 15 years (body weight 58 and 37 kg) suffered from uncorrected (not repaired) congenital heart defects (VSD) complicated with severe pulmonary arterial hypertension (WHO functional class Ⅱ and Ⅲ) and PVR/SVR-1/1,3.Treatments approved for pulmonary arterial hypertension include: Sildenifil, Accupro, Aspirin, Propranolol.Clinical investigations include routine EHO, ECG, Chest x ray complex intracardial investigation including angiocardiography.Local independent ethics committee approved the procedure and protocol.Written informed consent was obtained from parents.Both patients received transcatheter stem cells infusion in both (left and right) pulmonary arteries and stem cells substrat delivery intrapulmnary (directly in pulmonar parenchyma upon and lower lobus of right lung) using transcutan approach under general anaesthesia.The method for preparation the bone marrow aspirat for transplantation was described previously in details.By using method of scintigraphy during the periods 6, 12 and 24 months after stem cells implantation the evaluation of progress for neo-or revascularisation was elevated and documented.The aim of this study is to assess the safety and efficacy of autologous bone marrow derived stem cells implantation intrapulmonary in children with severe pulmonary hypertension and intramyocardial implantation in children with dilated cardiomyopathy.Conclusions: We observed no side effects.The results are promising and we hypothesised that bone marrow derived progenitor stem cell transplantation is a safe method and might be used for the stabilization of the patient with pulmonary hypertension and heart failure to get the time for further treatment.