Analysis of preoperative risk factor for delirium is important to identify patients at risk of it after head and neck cancer surgery. This study shows the results of 257 cases with head and neck cancer surgery at Nippon Medical School Hospital. Postoperative delirium developed in 34 of 257 patients (13.4%). Incidence of it after major operation including free flap head and neck reconstruction was 25.4%. Risk factors were a history of psychiatric disease, poor cognitive state and postoperative respiratory dysfunction due to lung edema. From this point of view, we made an original predictive score using five criteria : male sex, psychiatric disease history, poor cognitive state, living alone and respiratory complication just after surgery. We suggest that this scoring method may be useful in the identification of high-risk patients and for planning further treatment for postoperative delirium.