The purpose of this study was to estimate the impact of commercial MRAC on the evaluation of dementia, especially in Alzheimer’s disease (AD). We combined ADNI-data and patients data. We multiplied 14 error map derived from commercial Atlas-based MRAC method and each 203 ADNI data after the same nomalization and smoothing. To clarify the statement of prediction of AD, PET score was calculated by using PALZ. The accuracy, sensitivity and specificity for the discrimination of AD-patients from the normal control was not so impaired by MR-AC (Original vs. Error; 83.2%, 83.3% and 83.1% vs. 81.3% [range 77.6-83.2], 82.6% [range 79.2-85.4%,] and 80.3% [range71.2-86.4%]).