Postoperative nausea and vomiting (PONV) is related with extended hospital day and risk factor of aspiration pneumonia. Postoperative patient controlled intravenous analgesia is related with postoperative nausea and vomiting. Selective 5-HT3 antagonist, Palonosetron, is the most recent medication for prevention of PONV. Purpose of our study is comparison of PONV preventive effect of palonosetron and combination of palonosetron and dexamethasone.