Falls were assessed for 3 months using a daily fall diary in 65 (30 dementia with Lewy bodies, DLB; 35 Alzheimer's disease, AD) dementia patients from a case register, diagnosed using operationalised clinical criteria, with established accuracy against post-mortem. Multiple falls (>5) occurred in 37% of DLB patients and 6% of those with AD, often resulting in injury. None of the standard risk assessment tools identified fallers, but they did identify multiple fallers. More detailed evaluation methods examining gait patterns, sway and neurovascular instability were not helpful. Multiple falls were associated with DLB, parkinsonism, previous falls, greater impairment of activities of daily living and older age. Falls are particularly common in DLB sufferers and may aid diagnosis. Treatment studies evaluating fall reduction strategies are a priority.