When a soft tissue mass in the bony wall of the paranasal sinus is present, it is difficult to make a distinction between tumor and inflammatory mass on CT. Fungal sinusitis may have soft tissue attenuation on the bony wall of the sinus, bony sclerosis, focal bony destruction, and calcific areas on CT. This is a report of four proven cases of fungal sinusitis, asperogillosis in 3 cases and mucormycosis in 1 case. All 4 patients had CT and one patient had MRI. On cT, bony sclerosis and destruction were well visualized in all cases. On MRI, mycetoma in the maxillary sinus was hypointense on T1 weighted images and more hypointense on T2 weighted images. Although CT appears to be the best modality for initial examination of the patient with sinusitis, the differentiation of fungal sinusitis from tumor mass or other entity may be better accomplished with MRI.