Background and aims. Third molar agenesis is a common finding across the world. Many studies have assessed third molar agenesis in different ethnicities and populations. However, there are no such studies in the Italian and Lebanese populations. Our study aims to evaluate the prevalence of third molar agenesis and study the pattern and distribution of agenesis in between genders in Italian and Lebanese Mediterranean populations and compare these findings with other global and Mediterranean populations’ studies. Methods. Retrospective chart review was conducted based on the history and orthopantomograms of adolescents aged 12 to 21 years to assess the agenesis of third molars in a sample of Italian and Lebanese populations by two experienced dental surgeons twice within 1 month. Descriptive and comparative tests were used to analyze the patterns of ageneses and make comparisons between the two samples. Results. 23.4% of the studied sample had at least one third molar agenesis; females were more likely to have two or more third molar agenesis than males, but neither sex predisposition for single third-molar agenesis was recorded. Both the Italian and Lebanese subgroups seemed to have similar results. The maxillary right third molar was the most common third molar to be absent. Two or more ageneses were more common than one third molar agenesis. Conclusion. Our Mediterranean population results fall within the range reported in the literature and corroborate with the global average prevalence.