Carcinomas arising in the maxillary sinus are challenging technical problems for radiotherapists due to the complexity of the regional anatomy and the close relations of the tumor to dose-limiting critical structures (eyes, optic nerves, optic chiasm, and brain stem). This study shows that an improvement in the dose distribution can be achieved with the use of three dimensional treatment planning and a combination of x-ray and proton beam arrangements. Although tumor coverage was identical when comparing dose distributions of X rays alone to X rays plus proton beam boost, the critical structures received less dose in the X rays plus proton beam plan. Because a superior dose distribution should yield an improved local control and reduced morbidity, a benefit in survival could be expected.