Due to the heterogeneous course of illness in individual cases, efficacy or "treatment-response" can not be measured in single patients; therefore a clinical distinction between response and non-response is not meaningful. Constructs which are valid for research projects become misnomers in clinical practice. To date there are two groups of antidementia drugs, memantine--an NMDA-receptor modulator licensed for the moderate to severe stages--and the cholinesterase inhibitors donepezil, galantamine, and rivastigmine, licensed for mild to moderate stages of Alzheimer's disease. These substances exert a moderate symptomatic effect on cognition and activities of daily living or clinical global impression, which corresponds to a parallel shift of the natural course of dementia. A low number of contraindications and few serious adverse events are the advantages of memantine. The extensive evidence for their efficacy and safety are the advantages of cholinesterase inhibitors. Symptoms of "cholinopathy" (a severe lack of acetylcholine) predict a favorable treatment response to cholinesterase inhibitors in groups of demented patients with attention deficit disorders, fluctuating course of illness, visual hallucinations, and superimposed states of confusion.