Background Cognitive deficits in patients with asymptomatic carotid stenosis have been reported. The ultimate mechanism of cognitive deficits remains unclear and might be related to subtle structural brain damage. Aims The aim of the present study was to evaluate the presence of subtle white and grey matter abnormalities associated with asymptomatic carotid stenosis. Methods Twenty-five patients with asymptomatic >= 70%/occlusion carotid stenosis and 25 healthy controls, matched for gender and age, underwent 3 Tesla brain magnetic resonance imaging. Gray and white matter macrostructural abnormalities were evaluated with voxel-based morphometry using SPM8 software. White matter microstructural abnormalities were evaluated with diffusion tensor images with the Diffusion Toolbox package and tract-based spatial statistics from FMRIB Software Library. Results We observed significant macro-and microstructural white matter abnormalities, and these findings were diffuse and symmetrical in both hemispheres. In contrast, gray matter atrophy was observed in the areas corresponding to the anterior circulation of the hemisphere ipsilateral to the carotid stenosis. Conclusions Patients with asymptomatic carotid stenosis have different patterns of gray and white matter abnormalities. While the white matter damage is diffuse, the gray matter atrophy is localized in the territory of anterior circulation ipsilateral to the stenosis. The role of asymptomatic carotid stenosis in the gray matter damage must be further investigated with longitudinal studies and comparison with neuropsychological evaluation.108 11971203