Alzheimer’s disease (AD) and cerebral small vessel disease (CVSD) both contribute to age-related cognitive decline but can be difficult to clinically distinguish at early stages. At mild cognitive impairment (MCI), we investigated brain MRI volumetric differences in white matter hyperintensities (WMH), frontal and temporal lobe volumes between neuropathologically defined groups of cerebral arteriolosclerosis alone (pARTE), AD alone (pAD), and mixed (ADARTE).