Objective:  Detect  whether  bone  erosion  or  destruction  alters  the ADC value while  discriminating benign from malignant sinonasal masses. Patients and methods: Twenty five patients were investigated and operated upon  in  this  study.  Preoperative CT  scans  and  diffusion weighted MRI imaging were done within 48 hours prior to surgery. Surgical procedures were done in the form of complete resection or biopsy taking.  The  ADC  values  were  calculated  for  sinonasal lesions associated with bone erosion or destruction detected on CT scanning.   Results:  Histopathological  diagnosis  revealed  benign  masses  in 44%  and  malignant  tumors  in  56%  of  biopsies.  No significant differences between mean ADC values of the first and second ROI in both benign (P value =0.365) and malignant masses (P value =0.07). Statistical significant difference was found between the ADCL values of benign and malignant sinonasal masses. (P value =0.044).    Conclusions:  Bone erosion  or  destruction  does  not  alter  the  ADC  value  in differentiating  between  benign  and  malignant  masses. ADC value does not change with bone erosion or destruction.