In this study we analyzed the mandibular cortical bone of patients with type 1 diabetes mellitus (T1DM) and non-diabetic. Fifty patients with T1DM and 100 non-diabetic ones paired by age and gender were analyzed. Two double-blinded observers evaluated 150 digital panoramic images of both groups. The mandibular cortical bone was analyzed using the Mandibular Cortical Index (MCI), Mental Index (MI), Gonial Index (GI), Antegonial Index (AI) and Upper and Lower Panoramic Mandibular Indexes (UPMI and LPMI), with the aid of RADIOIMP ® software. Influence of T1DM in the morphology of the mandibular cortical bone was studied based on obtaining data related to T1DM diagnosis time, blood glucose level, T1DM control and the presence of chronic complications. Collected data were submitted to descriptive (mean and standard deviation) and inferential analyzes (Pearson's chi-squared test and Fisher's exact test) (p≤0.05). According to the MCI, individuals with T1DM had higher frequencies of mandibular cortical alterations, in both sexes and all age groups (p<0.01). For quantitative indexes, MI, GI, AI, UPMI and LPMI, female patients showed statistically significant differences for GI and AI, while male patients had statistically significant differences for all indexes (p<0.05), presenting the individuals with TDM1 inferior measures. Individuals with poor T1DM control showed significantly higher frequency of mandibular cortical alteration (92.3%), with lower means for MI, GI, AI and LPMI (p≤0.05). In conclusion, patients with T1DM showed decrease in the mandibular cortical bone when compared to non-diabetic ones, indicating that poor disease control is associated with these alterations.