Abstract： Objective To explore the features of inflammatory pseudotumor in the maxillary sinus on CT and MRI.Methods The CT and MRI data of 8 patients with histology-proven inflammatory pseudotumor in the maxillary sinus were retrospectively analyzed.All 8 patients underwent CT scans and 7 of them also underwent MRI examinations.In addition, the time-intensity curve (TIC) of dynamic contrast-enhanced (DCE)MR imaging were analyzed in 3 patients.Results Two cases had lesions in the left maxillary sinus, while the others showed lesions in the right maxillary sinus.All the lesions showed irregular shape with well-defined margins in 5 cases and hazy margins in 3 cases.The mean maximum diameter of the lesions was 51 mm (ranged from 29 mm to72 mm).On non-enhanced CT, the lesions were isodense to gray matter in 6 and slightly hypodense in 1 patients.Only 2 patients had post-contrast CT with moderate enhancement of their lesions.The lesions caused adjacent bony absorption and destruction with residual bony sclerosis.On MR T_1 WI, inflammatory pseudotumor showed hypointense in 2 patients and isointense in 5 cases in relative to gray matter.On T_2 WI, the lesions revealed inhomogeneous hypointense in 6 patients and isointense in 1 patients.Inflammatory pseudotumor showed heterogeneously slight contrast enhancement in 2 cases and moderate enhancement in 5 cases.The TIC showed a steady enhancement pattern in 3 patients.The lesions extended to nasal cavity in 6 cases, pterygopalatine fossa and infratemporal fossa in 4, orbit in 4, and cheek in 3 cases.Six patients underwent follow-up for 2-5 years after surgery and 2 of them were found to have recurrence.In comparison to CT, MRI was proved to show the extent of the lesions more clearly.Conclusions Bony destruction with sclerosis and hypointense signal on MR T_2 WI are typical manifestations of inflammatory pseudotumor in the maxillary sinus.Combined CT and MRI can provide clinicians with more comprehensive information for the diagnosis, therapy, and follow-up of these lesions.