To evaluate the prevalence and the characteristics of jaw lesions diagnosed in young adults aged 20 to 30 years in a southern Brazil reference center, over a period of 25 years. And to analyze the concordance between clinical and histological diagnosis. In this cross-sectional retrospective study, the biopsies files from this center were retrieved and data regarding sex, age, bone localization, clinical and histological diagnosis were collected. The histological diagnosis were grouped into the categories Cystic lesions of odontogenic origin, Periapical inflammation, Odontogenic tumors, Bone diseases, Health tissue and Nonspecific diagnostic. Absolute and relative frequencies were estimated with descriptive analysis. The agreement between clinical and histological diagnosis was measured through Kappa statistic. A total of 18,181 histopathological analysis were performed during the period of the study, registering 1,599 jaw lesions in young adults. The average age of individuals was 24,59 years (SD 3,1). Nine hundred ninety-one (62%) lesions were found in females and 608 (38%) in males. More than half of pathologies were cystic lesions of odontogenic origin (822/51.4%), followed by periapical inflammation (282/17.6%). Regarding the site of lesions, more than half occurred in posterior mandible (877/54.8%), followed by posterior maxilla (339/21.2%). The most frequent entities were periapical cyst, chronic periapical granuloma, dental follicle and paradental cyst, corresponding to a total of 1,202 (75.2%) evaluated cases. In relation to the analysis of concordance between clinical and histological diagnosis the general Kappa index was 0.5, which is considered moderate. Finally, the findings confirm data from literature about the most frequent jaw pathologies in young adults and serve as aid for preventive measures of some entities. Additionally, they can improve the formulation of differential diagnosis and the patient management.