Objective To analyze the CT and MR manifestations and the diagnosis of primary malignant melanoma in the nasal cavity and paranasal sinuses.Methods CT,MR features and clinical data of 1 6 cases of malignant melanoma in the nasal cavity and paranasal sinuses,which were confirmed by biopsy or surgical pathology and immunohistochemistry were analysed retrospectivelly. CT routine and enhanced scan were performed in all patients,MR routine and enhanced scan were performed in 9 cases.Results CT findings of 1 6 patients were unilateral,in which 8 cases were located in the nasal cavity,4 cases in the paranasal sinuses,and 4 cases were both in the nasal cavity and paranasal sinuses.All lesions were irregular shape with soft tissue densityand without calcification and cystic degeneration and demonstrated invasiveness to the surrounding tissue.Lesions were nonuniformly moderate to severe en-hancement.Among 9 patients with MR examination,lesions were mainly unilateral in which 4 cases were in the nasal cavity,3 cases in the paranasal sinuses,2 cases both in the nasal cavity and paranasal sinuses.Lesions were irregular in 9 cases,in which 1 case had typical high signal on T1 WI,low signal on T2 WI,while 3 cases equal signal on T1 WI,equal or slightly higher signal on T2 WI and 5 cases mixed signal.On MR enhanced scan,unevenly slight-medium enhancement were showed in the lesion and surrounding tissues. Conclusion Primary malignant melanoma of the nasal cavity and paranasal sinuses is lack of specificity on CT imaging.Typical ma-lignant melanoma,a type of rare to finding,has certain characteristics on MR,non-pigment type and mixed type are more common. CT combined with MRI can better show the site of the tumor,and the relation with surrounding tissues and adjacent bones.