Alzheimer's disease (AD) and vascular dementia (VaD) are the two most common causes of dementia in old people. They remain difficult to differentiate in practice because of lack of sensitivity and specificity of current clinical diagnostic criteria. Recent molecular and cellular advancements indicate that the use of cerebrospinal fluid markers may improve early detection and differential diagnosis of AD. Our objective in this study was to determine diagnostic accuracy of three cerebrospinal (CSF) markers: total tau protein (t-tau), tau protein phosphorylated on threonine 181 (p-tau181) and tau protein phosphorylated on serine 199 (p-tau199). Using commercially available ELISA kits concentrations of t-tau, p-tau181 and p-tau199 were analyzed in 12 patients with probable AD, 9 patients with VaD and 12 NC subjects. The median levels of all three markers were significantly higher in AD group versus VaD and NC groups. However, when the sensitivity levels were set to 85% or higher, only t-tau and p-tau199 satisfied consensus recommendations (specificity more than 75%) when differentiating AD from VaD. In conclusion, our preliminary data on a small group of selected subjects suggest that the CSF t-tau and p-tau199 levels are useful markers for differentiating AD from VaD.