Dementia with Lewy bodies (DLB) is the second most common form of neurodegenerative dementia. It is usually caused by a mixture of symptoms of Parkinson's and Alzheimer's disease leading to a significant impairment of nigro-striatal dopaminergic and baso-cortical cholinergic neurotransmission with typical clinical symptoms of a fluctuating course, hallucinations, parkinsonism, REM-sleep disorder and neuroleptic hypersensitivity. If the clinical presentation of DLB is uncharacteristic, the demonstration of reduced presynaptic striatal dopamine transporter (DaT) sites supports a suspicion of DLB and may lead to important therapeutic consequences. In these circumstances this evidence for compromised dopaminergic neurotransmission also indicates a significant cholinergic deficit: both require diligent therapeutic attention.