This study is aimed to determine the prevalence of impacted third molars and to investigate the effects of their eruption level and angulation on caries formation in the distal of the adjacent tooth. This cross-sectional study was conducted on panoramic radiographs of 38481 patients who were admitted to the Trakya University, Faculty of Dentistry. The panoramic radiographs of 7998 patients with at least one impacted third molar were included. Third molars were classified according to Winter?s classification and Pell and Gregory?s classification. The frequency of caries in partially impacted third molars and adjacent second molars was determined. The chi-square tests were used to determine potential associations between the third molars' level of eruption, angulation, and caries development. The study group consisted of 4423 females (55.3%) and 3575 males (44.7%) with a mean age of 36.3±13.4 years. The prevalence of the third molar impaction rate was 23%. The impaction pattern of partially erupted third molars was characterized by an eruption level of A with the vertical position in both jaws. Partially erupted and vertically placed maxillary third molars in the level of position A caused more caries in the adjacent tooth and mesioangularly located partially erupted mandibular third molars were associated with more caries in the adjacent tooth. The angulation and eruption level of partially erupted third molars should be carefully examined. The prophylactic extraction of vertically and mesioangularly located third molars, especially with an eruption level of position A can be suggested to eliminate the related complications and risk of caries.