OBJECTIVE To evaluate the relative value of magnetic resonance (MR) imaging versus computed tomography (CT) in the diagnosis of inflammatory paranasal sinus disease. METHODS In 30 patients suspected of having or known to have inflammation of the paranasal sinuses, both coronal CT and coronal T1-weighted, three-dimensional, gradient-echo MR imaging of the paranasal sinuses were performed. Visualization of anatomic details, kind and extent of inflammatory disease, and artifacts from dental work were scored. The scores were compared by using the Wilcoxon matched pairs signed rank test. Interexamination agreement between the two methods was calculated by using a kappa analysis. RESULTS Most bone structures of the infundibular complex were significantly better visualized at CT than at MR imaging. Orbital and brain anatomy were visualized better at MR imaging than at CT. No artifacts from dental work occurred in diagnostically relevant regions at MR imaging. There was a substantial to almost perfect agreement between CT and MR imaging for every kind and extent of the disease except for mucosal thickening in the maxillary and frontal sinuses, in the nasal cavity, and in the infundibulum. CONCLUSIONS CT is superior to MR imaging in the depiction of fine bony details and anatomic variants and thus is superior to MR imaging in helping plan functional endoscopic sinus surgery. However, there are patient groups in which MR imaging can be used as a primary tool in screening for sinusitis.