This study aimed to assess the relationship between skeletal malocclusion and radiomorphometric indices of the mandible in long face patients. This cross-sectional study evaluated 174 lateral cephalograms and panoramic radiographs of long face patients between the ages of 17 and 30 presenting at the Orthodontics Department of Qazvin Dental School. The gonial angle, antegonial angle, type of antegonial notch, and depth of antegonial notch were measured bilaterally on panoramic radiographs. The correlation between the radiomorphometric parameters and the type of occlusion was analyzed using one-way ANOVA, independent t-test, Chi-square test, and Fisher’s exact test (alpha = 0.05). The mean size of gonial angle was significantly different among the three classes of occlusion (p = 0.046), while the difference was not significant regarding the antegonial angle size and antegonial notch depth (p > 0.05). An independent t-test showed that the mean sizes of gonial angle (p = 0.026) and antegonial angle (p = 0.036), and the antegonial notch depth (p = 0.046) in males, were significantly greater than the values in females. According to the Chi-square and Fisher’s exact test, the right antegonial notch type was significantly different among the three classes of malocclusion (p = 0.006), while this difference was not significant in the left side (p = 0.318). The right antegonial notch type II was more common in males, while the right antegonial notch type I was more common in females (p = 0.014). According to the results, the indices of gonial angle and type of antegonial notch can be clinically useful for predicting the growth rate of the mandible and designing the appropriate treatment in long face patients.