This project assessed the contributions of atrophy and cerebrovascular disease (CVD) to cognitive impairment in dementia. Ten individuals with clinically diagnosed pure VaD were age-, sex-, and education-matched to individuals with AD. All participants underwent neuropsychological testing and MRI which were processed to generate quantitative indices of atrophy and CVD. A linear regression, including thalamic lesion and vCSF volumes, predicted cognitive status (R2 = .74; p < .0005). Three VaD subgroups were identified: thalamic lesion (n = 4), hippocampal infarcts (n = 3), and other (n = 3). In participants without thalamic lesion, vCSF predicted general cognition (R2 = .48), hippocampal atrophy predicted memory impairment (R2 = .33), and white matter lesions predicted executive dysfunction (R2 = .48). Both atrophy and CVD burden correlated highly with cognitive impairment and should be simultaneously assessed in studies of brain-behaviour relations in dementia.