Preferred embodiments of the present invention provide an apparatus and method for providing information needed for dementia diagnosis. In the apparatus and method in accordance with preferred embodiments of the present invention, an MRI brain image and a PET brain image of a subject for diagnosis are received, the MRI brain image is divided into a plurality of regions, and then the MRI brain image is registered with the PET brain image. Then, a standardized uptake value ratio of each divided region is obtained from the registered image, and for each divided region, a standard value indicating the degree of proximity of a standardized uptake value ratio of the subject for diagnosis to the average value of the standardized uptake value ratios of the group of the Alzheimer's patients and the average value of the standardized uptake value ratios of the normal group, which are stored in advance, is obtained.