The recent volumetric neuroimaging studies in children with fragile X syndrome, Down syndrome (DS), Rett syndrome (RS), and Tourette syndrome (TS) were reviewed. Neuroimaging studies and cognitive and behavioral phenotypes pertinent to each disorder were reviewed within the context of current knowledge of their neurobiological mechanisms. The mainly involved brain regions in fragile X syndrome are the cerebellar vermis, temporal areas, and the caudate nucleus which may be related to autistic tendency, problems of memory and language and deficits in executive function, respectively. The preferential involvement of frontal lobe, cerebellum and mesial temporal areas may correspond to the selective language and speech deficits in DS children. There was significantly generalized cerebral volume reduction with greater loss of gray matter in comparison to white matter, consistent with the extensive clinical features of RS. Right side predominance of basal ganglia supported the suggestion that the basal ganglia is related to pathogenesis of TS, which may also be related to the impaired executive function and the absence of functional asymmetry. Further prospectives for integrating neuroanatomic findings and neurobehavioral studies also were discussed.