Background: Preoperative assessment of mandibular bone invasion in squamous cell carcinoma of the oral cavity and oropharynx is crucial for optimizing bone resection. The principal aim of this study was to evaluate the diagnostic value of CT and MR imaging for the diagnosis of mandibular bone invasion compared to the histological reference. In addition, we assessed the survival impact of bone invasion. Patients and methods: A single-center retrospective study included all consecutive patients treated by mandibular bone interruption for squamous cell carcinoma of the oral cavity and/or oropharynx. Results: Sixty-eight patients were included. Prevalence of bone invasion on histology was 43%. Sensitivity, specificity and positive and negative predictive value were respectively 70%, 71%, 66% and 76% for CT compared with histologic analysis, 83%, 50%, 59% and 78% for MRI, and 83%, 62% 62%, 83% for associated CT and MRI. The two tests showed good agreement, with kappa index 0.69 (95% CI, 0.49-0.89) (P<0.0001). There was no difference in overall survival (log-rank>0.70) between the groups with and without bone invasion. Conclusion: CT and MRI are complementary for preoperative assessment of mandibular bone invasion, be it cortical and/or medullary, and in some cases may allow mandibular bone-sparing.