Introduction[ Sleep disturbances are common in healthy old age and in dementia syndromes[ Polysomnography has demonstrated typical changes in both Alzheimer|s disease "AD# and dementia with Lewy bodies "DLB# with AD being characterised by sundowning and sleep apnoea and DLB patients showing more disturbances of movement control during sleep[ The technical di.culties associated with EEG sleep recordings mean that polysomnography is not possible out of specialist centres[ Objectives[ To use questionnaires to assess the frequency of sleep disturbances in patients with Alzheimer|s disease and dementia with Lewy bodies[ Method[ The sleep pro_les of twenty patients with AD and 06 with DLB were assessed using three questionnaires\ one designed to assess night time sleep disturbance\ one day time sleepiness and the last carer burden[ The sleep questionnaires were repeated in a subgroup after treatment with a cholinesterase inhibitor "rivastigmine#[ Results[ Level of sleep disturbance in both groups was high[ DLB patients had more overall sleep disturbance\ more movement disorders whilst asleep and more abnormal day time sleepiness[ Treatment with rivastigmine produced a trend towards normalisation of sleep pro_le in a small number of subjects[ Conclusions[ Both groups have extensive sleep problems[ The DLB and AD groups have di}erent sleep pro_les that are of diagnostic importance and may suggest di}erent treatment strategies[ The results are consistent with those found from polysomnographic assessment and suggest that the questionnaires used are sensitive to detect di}erences previously documented with polysomnography[