Objective To find better diagnostic methods and criteria by re-evaluation for initial clinical dementia diagnosis. Methods Totals of 22 subjects diagnosed as mild neurodegenerative non-vasculardementia from June 2011 to June 2012 were included. Brain PIB and FDG PET，CSF test and neuropsychological tests were assessed in all patients. MMSE test was measured every 1-2 years untill April 2017. Results The diagnosis of 7 out of 22 subjects was changed. 4 patients diagnosed with Alzheimer disease （AD）changed to dementia with Lewy bodies （DLB），while 2 AD patients and 1 behavioural variant frontotemporal dementia （bvFTD）patientchanged to unspecified dementia （UNS）. There were significant differences between changed and non-changed team in educational level，Aβ42 concentration，comprehension test，episodic memory test and reductions in regional cerebral glucose metabolism（P＜0.05）. Conclusions Brain PET imaging and CSF test have guiding significance for re-evaluation for clinical dementia diagnosis.