Dementing disorders belong to the most frequent neuropsychiatric diseases of the elderly population with prevalence rates of 5% in the 75 year old, but more than 10% in subjects older than 80 years. It is broadly accepted that the dementias are not caused by a single etiological factor but are attributed to a variety of different disease processes that affect the brain either directly or indirectly. Accbrding to pathoanatomic studies, two thirds of all dementias are caused by Alzheimer's disease (AD). Early recognition and differential diagnosis, Which represent an important prerequisite for an optimized therapy, can be facilitated considerably by neuroimaging as well as by molecular biological findings. Therapeutic approaches include general medical managment, psychosocial interventions as well as pharmacotherapy of cognitive and non-cognitive deficits. In general, early intervent using a combination of different therapeutic measures is recommended. In future, structural and functional neuroimaging might not only be used for, diagnostic purposes but also to objectify and monitor the effect of treatment on relevant brain, structures.