This review presents diagnostic criteria for the different dementia syndromes and mild cognitive impairment. It is being claimed that in view of the current pharmacological interventions and after exclusion of symptomatic dementia, a controlled trial with cholinesterase inhibitors or memantine is more efficient than elaborate diagnostics. Efficiency of differential diagnosis will increase when drugs are available that specifically improve the different degenerative dementias and vascular dementia. Clinical pictures of the various dementia syndromes are briefly described.