The article reviews sex differences in brain structure, function, and chemistry in healthy individuals using neuroimaging techniques such as fMRI, PET, SPECT, and MRI. It highlights that while there are similarities in brain structure, function, and neurotransmission between men and women, important differences exist. Men generally have larger brain volumes, but when adjusted for total volume, women have a higher percentage of gray matter and men a higher percentage of white matter. Regional volume differences are less consistent. Women have higher global cerebral blood flow than men. Sex-specific differences in dopaminergic, serotonergic, and GABAergic markers indicate that male and female brains are neurochemically distinct. These differences may influence the prevalence and course of psychiatric disorders and the effectiveness of treatments. The review emphasizes the importance of considering sex differences in brain structure, function, and neurochemistry to better understand and treat neuropsychiatric disorders. It also notes the need for further research to account for factors such as the menstrual cycle and hormonal influences in studies of brain differences between men and women.The article reviews sex differences in brain structure, function, and chemistry in healthy individuals using neuroimaging techniques such as fMRI, PET, SPECT, and MRI. It highlights that while there are similarities in brain structure, function, and neurotransmission between men and women, important differences exist. Men generally have larger brain volumes, but when adjusted for total volume, women have a higher percentage of gray matter and men a higher percentage of white matter. Regional volume differences are less consistent. Women have higher global cerebral blood flow than men. Sex-specific differences in dopaminergic, serotonergic, and GABAergic markers indicate that male and female brains are neurochemically distinct. These differences may influence the prevalence and course of psychiatric disorders and the effectiveness of treatments. The review emphasizes the importance of considering sex differences in brain structure, function, and neurochemistry to better understand and treat neuropsychiatric disorders. It also notes the need for further research to account for factors such as the menstrual cycle and hormonal influences in studies of brain differences between men and women.