Early identification of those at higher risk of dementia may play a part in secondary prevention and has received great clinical and research interest. Mild cognitive impairment (MCI) is a construct originally proposed to identify those who fall between normal cognitive aging and dementia. Clinical and research utility and validity of MCI are hotly debated. New MCI criteria proposed include the recent construct of mild neurocognitive disorder in the 5th edition of the Diagnostic and Statistical Manual of Mental Disorders, MCI criteria proposed by the National Institute on Aging-Alzheimer's Society and criteria elaborated by the International Working Group. This article aims to discuss whether these definitions provide clearer conceptualization of MCI and to highlight implications for research.