Background/Aims: The aims of this study were to validate the newly developed version of the Addenbrooke's Cognitive Examination (ACE-III) against standardised neuropsychological tests and its predecessor (ACE-R) in early dementia. Methods: A total of 61 patients with dementia (frontotemporal dementia, FTD, n = 33, and Alzheimer's disease, AD, n = 28) and 25 controls were included in the study. Results: ACE-III cognitive domains correlated significantly with standardised neuropsychological tests used in the assessment of attention, language, verbal memory and visuospatial function. The ACE-III also compared very favourably with its predecessor, the ACE-R, with similar levels of sensitivity and specificity. Conclusion: The results of this study provide objective validation of the ACE-III as a screening tool for cognitive deficits in FTD and AD.