Dementia is frequent in the elderly, and advancing age is the strongest risk factor. It includes Alzheimer's disease (AD), Vascular dementia (VaD), and other neurogenerative disorders such as Lewy body dementia (LBD), and other less-common neurodegenerative dementing diseases, such as frontotemporal dementia (FTD). All this acquired disorder of cognition and the related behavioral impairment interferes with social and occupational functioning. The fourth edition of the Diagnostic and Statistical Manual of Mental Disorders (DSM-IV) and the fifth edition of the Diagnostic and Statistical Manual of Mental Disorders (DSM-V) present differences in the description of AD and VaD. The new DSM recognizes the acceptable alternative "neurocognitive disorder" as a newly preferred and more scientific term than "dementia". This new diagnosis includes both the dementia and amnesic disorder diagnoses from DSM-IV. Furthermore, DSM-V recognizes specific etiologic subtypes of neurocognitive dysfunction, such as Alzheimer's disease, Parkinson's disease, HIV infection, Lewy body disease, and Vascular disease. This is a review based on scientific evidence and information concerning the most common dementia, Alzheimer's disease (AD) and the second most important, Vascular dementia (VaD), and the main differences between the classifications of DSM-IV and DSM-V for both diseases.