Objectives. Early and accurate diagnosis of Dementia with Lewy Bodies (DLB) to allow the appropriate clinical treatment is a priority, given reports of severe neuroleptic sensitivity and a preferential response to cholinesterase inhibitors in these patients. There have been suggestions that constructional apraxia is prevalent in DLB, and may provide a sensitive marker of the disease. Methods. This study examined the pentagon drawings of 100 DLB patients, 50 Alzheimer's disease (AD) patients, 81 Parkinson's disease (PD) patients of whom 36 suffered from dementia (PDD). Performance on this task was correlated with cognitive performance on the MMSE and CAMCOG scales. Results. Patients with DLB were found to draw significantly worse pentagons than those with AD or PD, but not those with PDD. Drawing scores were significantly correlated with MMSE scores for the AD and PDD groups but not those with DLB. More detailed analysis of the neuropsychological correlates of constructional performance for patients with AD and DLB, revealed that those with AD showed a broad cognitive basis to their impairment, in DLB drawing was linked only to perception and praxis. Conclusions. This study has suggests that DLB subjects show an impairment of pentagon copying that is dissociable from more global cognitive impairments, whereas PD patients are relatively unimpaired on pentagon copying and AD and PDD patients show a linkage of their impairment in copying with more global cognitive deficits.