The differentiation between cortical and subcortical dementias requires that the cognitive characteristics of dementias attributable to different causes be discriminable. For large samples of Alzheimer's disease and Huntington's disease patients, distinct cognitive profiles were obtained on the Mini-Mental State Exam. The profile differences were independent of severity of dementia and were sufficiently robust to classify patients as Alzheimer's disease or Huntington's disease with 84% accuracy. The qualitative differences in cognitive functioning may also be typical of other cortical and subcortical dementias.