As the first and second most prevalent causes of dementia, Alzheimer disease dementia (ADD) and dementia with Lewy bodies (DLB) lie at opposite ends of what can be called, for want of a better term, a temperamental spectrum. ADD, at least in its earlier stages, is a quiet dementia. While early reports of Lewy body pathology date back to 1912, DLB has been recognised as a specific and distinct dementia subtype for just over two decades. Pathologically, DLB is characterised by the presence of Lewy bodies. Cortical atrophy is generally less severe and extensive in DLB than in Alzheimer’s disease (AD). Grey matter atrophy in DLB is predominantly found in temporal, parietal, occipital, and subcortical structures relative to normal controls, and there is less mesial temporal atrophy than is typically found in AD. Unlike its nearest epidemiological neighbour, AD, DLB is a more florid condition, characterised by neurological, neuropsychiatric, neurocognitive, and autonomic features.