PURPOSE: To compare intensity-modulated radiotherapy (IMRT) treatment planning with three-dimensional conformal radiotherapy (3D-CRT) planning for paranasal sinus carcinoma. MATERIALS AND METHODS: Treatment plans using traditional 3-field technique, 3D-CRT planning, and inverse planning IMRT were developed for a case of paranasal sinus cancer requiring adjuvant radiotherapy. Plans were compared with respect to dose conformality, dose-volume histograms, doses to critical normal tissues, and ease of treatment delivery. RESULTS: The inverse-planned IMRT technique was more conformal around the tumor target volume than conventional techniques. The dose-volume histograms demonstrated significantly better critical normal-tissue sparing with the IMRT plans, while able to deliver a minimum dose of 60 Gy to the clinical tumor volume and 70 Gy to the gross tumor volume. Acute toxicities in our analysis were minimal. CONCLUSIONS: IMRT planning provided improved tumor target coverage when compared to 3D-CRT treatment planning. There was significant sparing of optic structures and other normal tissues, including the brainstem. Inverse planning IMRT provided the best treatment for all paranasal sinus carcinomas, but required stringent immobilization criteria. Further studies are needed to establish the true clinical advantage of this modality.