Dementia (the most common cause of Alzheimer's disease) is defined as a chronic or progressive syndrome with disturbance of multiple cortical functions, the most important of them including memory, learning capacity, comprehension, orientation, calculation, language, and judgement. These cognitive impairments affect the quality of life, behavior, and social relations. Techniques of nuclear medicine provide feasible ways to record the intracellular alterations of disease and deficiencies. In these non-invasive manners, the hippocampal-neocortical disconnection may partly explain the hypo-metabolism incident found in Alzheimer's disease. Based on this fact, the study of all these mechanisms of action is conceivable and achievable by radiopharmaceuticals. This review is aimed at the presentation of radiopharmaceuticals that are developed for the detection of Alzheimer's disease in preclinical and clinical trials.