The two commonest causes of dementia are probably dementia of the Alzheimer type (DAT) and dementia with Lewy bodies (DLB), and although their pathology is relatively well characterised (albeit controversial in terms of diagnostic features) the clinical expression of these disorders can sometimes be difficult to distinguish. Typically DAT presents with deficits in episodic memory with language involvement whereas in DLB it is more hallucinations with a fluctuating dementia in the context of a parkinsonian syndrome. Distinguishing these two disorders, however, is not always straightforward and in this issue (pp583–588) Yoshito et al 1 claim that such a distinction can be …