Background: To evaluate the pattern of impaction of third molar in a known population. Materials & methods: There were 100 panoramic radiographs included in the study. According to Pell and Gregory's classification, the depth of impaction as well as the location of the impacted third molar on the mandible in relation to the mandibular ramus were found. Chi-square analysis was used to examine the data. SPSS software was used for the analysis of the results. Results: The frequency distribution of level of mandibular third molar impaction in the right and left sides. Level C was the most common depth of impaction in both the right (47.14%) and left (56.67%) sides. There was no association between the side and the impaction depth (p=0.5). Conclusion: The level C and Class I impaction patterns were the most frequent. Keywords: third molar, impaction, pattern.