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.