Objective The aim of this study was to examine the relationship between ramus height, gonial angle and impaction classifications of mandibular third molars. Methods A total of 829 mandibular third molars in 601 patient's orthopantomography (OPG) and cephalometric radiography records were evaluated. Gonial angle was measured on cephaloametric radiography and ramus height was measured on OPG. Impacted third molars were classified according to Pell & Gregory Vertical/Winter classification on OPG. The relationship between the impaction classifications and ramus height/gonial angle was evaluated. Results Statistically significant difference was found in Pell & Gregory Classification types in terms of ramus height/gonial angle (p < 0.001). Significant difference was found in terms of Gonial angle in Winter Classifications (p < 0.001). Ramus height was found to be lower than 3.8 cm in patients with an angle less than 123.8 degrees (sensitivity 78%, specificity 84%). Conclusions Correlation between ramus height/gonial angle and impaction classification types of mandibular third-molar teeth was detected.