Background: Magnetic resonance imaging has become the most accurate technique in local staging of rectal cancer. The identification and staging of rectal cancers at MR imaging is largely based on differences in T2 signal intensity between the tumor, the mucosa and submucosal layers, the muscular layer, the perirectal fat, and the mesorectal fascia. Objective: Was to assess the role of Diffusion Weighted MRI in assessment of rectal cancer and correlation of these findings with available histopathological findings. Patients and Methods: A total of 30 patients, proved by colonoscopy to have rectal carcinoma, were included in this retrospective study wich was carried out in the Radiology Department of Al-Azhar University Hospitals. The work took place during the period between June 2018 and Januray 2019.written consent was taken from each patient. The study was carried out after approval of the ethical committee of scientific research, faculty of medicine, Al-Azhar University. Results: we found that DW MRI measurement increased the specificity of the rectal MRI in characterizing different rectal cancers especially when it is combined with conventional MRI.Also the use of additional DW MR imaging yields better diagnostic accuracy than does use of conventional MR imaging alone in the evaluation of complete response (CR) to neoadjuvant chemoradiation treatment (CRT) in patients with locally advanced rectal cancer. Conclusion: DW MRI has a growing role in rectal cancer staging either primary staging or evaluating the post chemo radiotherapy state.