Abstract Disclosure: A.A. Bastos: None. A.P. Machado Canton: None. L.B. Macena: None. L.F. Pedrosa: None. B.B. Mendonca: None. V.N. Brito: None. A. Latronico: None. Introduction: Brain magnetic resonance imaging (MRI) is the main tool used to investigate the etiology of central precocious puberty (CPP) in children. A systematic review study showed an overall prevalence of 9% of brain lesions in girls with CPP. Aim: To assess the frequency brain lesions in children with CPP. Patients and Methods: In this retrospective study, we recruited data of 163 brain MRI of children with CPP (140 girls,86%; and 23 boys, 14%) followed in a pediatric endocrinology unit from 1990 to 2022. Brain lesions were classified as congenital or acquired, and causative of CPP or incidental. Results: In girls, normal brain MRI was found in 82/140 (59%). Abnormal brain MRI was identified in the remaining 58 girls (41%), with 26 presenting congenital lesions causative of CPP (11 hypothalamic hamartoma, 7 hydrocephalus, 3 optic pathway gliomas, 2 corpus callosum agenesia, 1 pinealoma, 1 tuberous sclerosis, 1 choroid plexus papilloma), and 32 with incidental findings (microadenomas, pituitary stalk deviation, pituitary hyperplasia, rathke cleft cyst, hippocampal alterations). The overall frequency of incidental findings was 20.8%. In addition, the frequency of brain MRI pathological abnormalities in girls older than 6 years without neuro ophthalmological symptoms was 12%(n=7). In boys, normal brain MRI was found in 6/23 (26%). Abnormal brain MRI was identified in the remaining 17 boys, with 14 presenting congenital lesions causative of CPP (9 hypothalamic hamartoma, 4 hydrocephalus, 1 pineal teratoma) and 1 with acquired lesions (1 pilocytic astrocytoma). Incidental findings were detected in only 2 brain MRI (1 pineal cyst and 1 microadenoma). Incidentalomes were more frequent in girls and lesions that can be associated with CPP were more common in boys. Conclusion: The frequency of pathological brain lesions was higher in CPP boys. Hypothalamic hamartoma was the most frequent congenital lesion identified in both sexes. Based on the frequency of pathological brain alterations in girls older than 6 years we recommend to perform brain MRI in all CPP girls. Presentation: Thursday, June 15, 2023