BACKGROUND In this study, we compared the treatment outcomes of postoperative 3D conformal radiotherapy (RT) and intensity-modulated radiotherapy (IMRT) for patients with maxillary sinus carcinoma. METHODS Fifty-four patients underwent surgery and postoperative RT, of whom 27 (50%) had squamous cell carcinoma and 14 (26%) had adenoid cystic carcinoma. Nineteen patients (35%) were treated with IMRT and 35 patients (65%) received 3D conformal RT. The median radiation dose for 3D conformal RT and IMRT were 62.1 and 63 Gy, respectively. RESULTS IMRT produced significantly superior radiation dose distribution to planning target volumes (PTVs) than 3D conformal RT. Over a median follow-up of 60 months, IMRT provided better 3-year locoregional recurrence-free survival (89.2% vs 59.5%; p = .035) and distant metastasis-free survival (94.7% vs 55.3%; p = .042) rates than 3D conformal RT. CONCLUSION Postoperative IMRT for patients with maxillary sinus carcinoma resulted in excellent disease control, and should be considered as the first treatment option in these cases. © 2015 Wiley Periodicals, Inc. Head Neck 38: E207-E213, 2016.