The invention provides a method for detecting or monitoring Alzheimer's disease and other forms of dementia using positron emission tomography (PET) or single-photon emission computed tomagraphy (SPECT) and radiolabeled, serotonin 5-HT.sub.1A receptor-specific tracers (such as [F-18]MPPF, [F-18]FCWAY, [C-11]WAY-100635, and other radiolabeled compounds having agonistic or antagonistic effect on serotonin receptors), for detection or monitoring of pathological changes (i.e., neuronal cell loss) associated with dementia.