Aim of the study is to evaluate whether Tc-99m-ECD-SPECT/CT enhances early diagnosis of dementia in two specific patient groups: (1) patient with mild cognitive impairment, and (2) patient with possible symptoms and signs of frontotemporal dementia. Evaluation of SPECT/CT data is performed both by visual and quantitative voxel-based analyses (Statistical Parametric Mapping). The final diagnosis is based on up to four years clinical follow-up.