Chronic thrombembolic pulmonary hypertension is a rare complication of acute pulmonary embolism. Narrowing or closure of pulmonary arteries is the cause of pulmonary hypertension and results in right ventricular overload and failure. The treatment of choice is pulmonary thrombendarterectomy. Deep hypothermic circulatory arrest is a very important factor required for complete removal of the thrombembolic material from the pulmonary arteries during the operation.The aim of the study was the evaluation of the effectiveness of the use of deep hypothermic circulatory arrest during pulmonary thrombendarterectomy in patients with chronic thrombembolic pulmonary hypertension.Material and methods. Between October 1995 and October 2006 seventy patients were operated on. All of them were operated on with the use of deep hypothermic circulatory arrest. Deep hypothermia (18-19°C), pharmacotherapy, and neuromonitoring were used as a protection of the central nervous system during circulatory arrest.Results. In fifty-seven patients out of seventy, complete thrombendarterectomy was performed (more than 75% of branches opened). The average pulmonary artery pressure and pulmonary vascular resistance were decreased, and cardiac output and index were increased. Six patients died (8.6%).Conclusions. Complete thrombendarterectomy gives significant hemodynamical improvement in patients undergoing the operation. Deep hypothermic circulatory arrest during the operation does not cause significant neurological complications. Incomplete thrombendarterectomy may be the cause of right ventricular failure and death after the operation.