Objective: To compare cerebralspinal fluid acetylcholine (ACh) and choline (Ch) in patients with Alzheimer's disease (AD) and vascular dementia (VD), and their correlation with cognitive impairment. Methods: First, dementia scales of 22 ADs, 22 VDs and 20 controls were scored using MMSE. Then the concentrations of CSF ACh and Ch in AD and VD were examined using the high-performance liquid chromatography with electrochemical detector (HPLC-ECD). Finally, the scores of MMSE and concentrations of ACh and Ch were compared. Results: The ACh concentrations in AD[(10.7 ± 5.1)nmol/L] and VD [(16.8 ± 7.4)nmol/L] were found to be significantly lower than in controls [(34.5±9.0)nmol/L] (P = 0.001), and showed a significant positive correlation with MMSE scores. The Ch concentration in AD CSF [(627.6 ± 145. 1)nmul/L] was approximately the same as in controls [(716.0 ± 159.4)nmol/L], and showed no correlation with MMSE scores. The Ch concentration in VD CSF [(887.4 ± 187.4)nmol/L] was significantly higher than in AD (P = 0.001) and controls (P = 0.002). Conclusion: (1) The depression of ACh is correlated with cognitive impairment, suggesting ACh is an important neurotransmitters for memory. (2) VD may have a similar pathogenesis as AD. (3) The depression of AD ACh concentration and elevation of VD Ch concentration in CSF may be a role in their differentiation. (4) The application of acetylcholinesterase inhibitors is suitable for AD and VD.