We carried out a quantitative analysis of transthyretin (TTR), total tau protein and amyloid-beta (Abeta) peptide (1-40 and 1-42) in the lumbar cerebrospinal fluid of 106 patients with different forms of dementia including Alzheimer's disease (AD), Creutzfeldt-Jakob-disease (CJD), dementia with Lewy bodies (DLB), frontotemporal dementia (FTD) and normal pressure hydrocephalus (NPH) in comparison to healthy controls. Our study revealed that Abeta_{1-42} levels were decreased in all patients irrespective of dementia type. Tau protein levels were abnormal in all degenerative dementia except of NPH. Tau levels did not allow differential diagnosis of dementia type except for CJD, where we observed extremely high CSF levels. In other dementia types, levels were elevated in a similar range. Transthyretin levels were selectively decreased in AD and NPH, thus revealing the potential of this protein to be used as additional biomarker in the neurochemical differential diagnosis of AD. A significant negative correlation of TTR CSF levels and disease severity in AD was observed.