We experienced anesthetic management for a patient with platypnea-orthodeoxia syndrome. This syndrome is relatively uncommon and accompanies dyspnea and hypoxemia on changing to a sitting or standing from recumbent position. A 75-year-old man with the syndrome underwent atrial septal defect closure on cardiopulmonary bypass. General anesthesia was induced and maintained with midazolam, propofol, fentanyl and vecuronium bromide. During the induction, Spo2 decreased suddenly from 100% to 70%, Spo2, however, recovered to 97% immediately after changing to Trendelenburg position. The perioperative and postoperative course was uneventful, except for hypoxemia during induction. Although the exact mechanisms of platypneaorthodeoxia remains to be solved, right-to-left shunt by an anatomical abnormality and by change of the atrial septum is considered one of the hypoxic mechanisms. We suggest that it is necessary to prevent right-to-left shunt and hypoxemia in anesthetic management of a patient with platypneaorthodeoxia syndrome.