This review explores the role of sex hormones in cerebrovascular development and neurodevelopmental disorders, focusing on autism spectrum disorder (ASD) and attention-deficit/hyperactivity disorder (ADHD). Proper cerebrovascular development and neurogliovascular unit assembly are essential for brain growth and function, involving key pathways such as vascular endothelial growth factor (VEGF) and Wnt signaling. These pathways are crucial for brain vascular growth, expansion, and blood-brain barrier (BBB) maturation. Sex hormonal dysregulation in early development has been implicated in neurodevelopmental disorders with sexually dimorphic features, such as ASD and ADHD. Both disorders show higher prevalence in men, with varying symptoms between sexes. Boys exhibit more externalizing behaviors, while girls display higher internalizing behaviors. High estrogen levels seem to attenuate ADHD symptoms, while high prenatal testosterone exposure and reduced aromatase expression may explain sex differences in prevalence and symptomatology. Sex- and region-specific variations in cerebral blood flow perfusion have been reported in both conditions, indicating an impact of gonadal hormones on the brain vascular system. The review highlights the interaction of gonadal hormones with brain vascular and BBB development, focusing on VEGF and Wnt signaling. It outlines how these pathways may underpin ASD and ADHD. Outstanding questions and potential avenues for future research are highlighted, emphasizing the need to understand sex-specific physiological and pathological aspects of brain vascular development to develop innovative therapeutic approaches for ASD, ADHD, and beyond. Keywords: Autism spectrum disorder, Attention-deficit/hyperactivity disorder, Neurovascular development, Neurovascular unit, Neurodevelopmental disorders, Gonadal hormones, Sex differences, Cerebral blood flow.This review explores the role of sex hormones in cerebrovascular development and neurodevelopmental disorders, focusing on autism spectrum disorder (ASD) and attention-deficit/hyperactivity disorder (ADHD). Proper cerebrovascular development and neurogliovascular unit assembly are essential for brain growth and function, involving key pathways such as vascular endothelial growth factor (VEGF) and Wnt signaling. These pathways are crucial for brain vascular growth, expansion, and blood-brain barrier (BBB) maturation. Sex hormonal dysregulation in early development has been implicated in neurodevelopmental disorders with sexually dimorphic features, such as ASD and ADHD. Both disorders show higher prevalence in men, with varying symptoms between sexes. Boys exhibit more externalizing behaviors, while girls display higher internalizing behaviors. High estrogen levels seem to attenuate ADHD symptoms, while high prenatal testosterone exposure and reduced aromatase expression may explain sex differences in prevalence and symptomatology. Sex- and region-specific variations in cerebral blood flow perfusion have been reported in both conditions, indicating an impact of gonadal hormones on the brain vascular system. The review highlights the interaction of gonadal hormones with brain vascular and BBB development, focusing on VEGF and Wnt signaling. It outlines how these pathways may underpin ASD and ADHD. Outstanding questions and potential avenues for future research are highlighted, emphasizing the need to understand sex-specific physiological and pathological aspects of brain vascular development to develop innovative therapeutic approaches for ASD, ADHD, and beyond. Keywords: Autism spectrum disorder, Attention-deficit/hyperactivity disorder, Neurovascular development, Neurovascular unit, Neurodevelopmental disorders, Gonadal hormones, Sex differences, Cerebral blood flow.