Objectives: • To assess the role of diffusion-weighted MR imaging in differentiating residual malignant lesions of tongue and buccal mucosa from post radiotherapy inflammatory changes in biopsy proven cases of carcinoma tongue and buccal mucosa. • To assess the predictive validity of ADC values in differentiating residual malignant lesions of tongue and buccal mucosa from post radiotherapy inflammatory changes in biopsy proven cases of carcinoma tongue and buccal mucosa. • To assess the diffusion weighed imaging (DWI) characteristics of malignant lesions of tongue and buccal mucosa. Methods : • Study design: It is a retrospective observational study • Study setting: Department of radiology of Vydehi Instititute of Medical Sciences and Research Centre . • Study population: Known cases of tongue and buccal malignancies, post radiotherapy and chemotherapy referred to the department of radiology to access for treatment response. • Sample size: A total of 18 eligible subjects were included. • The eligible patients underwent conventional MRI and DWI with b-values of 0 and 800 s mm−2 . The apparent diffusion coefficient (ADC) maps were reconstructed and the ADC values of the lesions were calculated and compared between post radiotherapy inflammatory changes and residual lesions of the tongue and buccal mucosa.