In order to demonstrate the clinical efficacy of prone positioning(PP), we reviewed 2 elderly patients with respiratory failure who underwent thoracic aortic surgery. Case 1:An 80-year-old man with true thoracic aortic aneurysm (TAA) underwent total arch replacement under moderate hypothermia. Two days after surgery, PP was conducted for 3 hours to treat atelectasis and poor oxygenation. His respiratory state and oxygenation subsequently improved and he was weaned from ventilator assistance. Case 2:An 82-year-old woman with early thrombosed acute type A aortic dissection and cardiac tamponade underwent emergency primary repair of the ascending aorta under moderate hypothermia. Six days after surgery, PP was conducted for approximately 3 hours to improve oxygenation. She was weaned from the ventilator 7 days after surgery. The clinical courses of both cases after PP were uneventful. In order to improve the respiratory state of elderly patients after TAA surgery, PP is effective and useful.