Dementia with Lewy bodies is the second most common form of neurodegenerative dementia, yet scarce evidence is available about its prognosis and natural history, which are crucial to inform clinical practice and research. Patients with dementia with Lewy bodies might have a less favourable prognosis, with accelerated cognitive decline, shorter lifespan, and increased admission to residential care than patients with Alzheimer's disease. Health-care costs and, importantly, caregiver burden, are also reported to be higher in dementia with Lewy bodies than in Alzheimer's disease. It is probable that causative factors for this less favourable prognosis are the increased prevalence and early emergence of neuropsychiatric symptoms in patients with dementia with Lewy bodies, and the challenge of accurate diagnosis. Evidence concerning quality of life and hospital admission rates is limited, despite their clinical and economic relevance.