Cholinesterase inhibitors (ChEIs) are effective in improving cognition and behavior in patients affected by Alzheimer's disease (AD) as well as by Lewy bodies dementia (DLB). The authors compared the effect of rivastigmine in the treatment of cognitive impairment and behavioral and psychological symptoms of dementia (BPSD) in 30 AD and in 30 DLB patients. At baseline, DLB compared to AD patients showed a greater number of extrapyramidal symptoms (P < .005) and were similar regarding cognitive symptoms and BPSD. After treatment, both groups showed a comparable cognitive and psycho-behavioral improvement. A significant difference between AD and DLB patients was found for hallucinations (P < .002). Rivastigmine produces comparable cognitive benefits in patients with DLB and AD and also a significant improvement of behavioral disorders. These findings support the view that ChEIs should be considered a first-line treatment of the cognitive and psycho-behavioral symptoms of both AD and DLB.