The aim of our work was to evaluate the early presence of white matter changes on magnetic resonance imaging (MRI) in young asymptomatic children of patients with full-blown cerebral autosomal dominant arteriopathy with subcortical infarcts and leukoencephalopathy (CADASIL) in whom DNA analysis revealed a Notch3 Cys146Tyr missense mutation on chromosome 19. Brain MRI was performed in all subjects using axial and coronal spin-echo proton density and T2-weighted images, axial fluid-attenuated inversion recovery (FLAIR) and sagittal and axial T1-weighted images. In asymptomatic subjects with Notch3 gene mutation, MRI showed small T2 hyperintense foci in periventricular and subcortical white matter. Routine use of MRI in the initial phases of a CADASIL diagnostic work up and the subsequent recognition of early abnormal findings in asymptomatic subjects may lead to prompt diagnosis of the disease in these patients. Moreover, these findings suggest that genetic screening is warranted in the presence of a suspect clinical history with specific MRI abnormalities.