Objective Given the rather limited knowledge on profiles of neuropsychiatric symptoms (behavioural and psychological signs and symptoms of dementia, BPSD) in several degenerative dementias, we designed a prospective study of which we here present the baseline data. Methods Diagnosed according to strictly applied clinical diagnostic criteria, patients with probable Alzheimer's disease (AD) (n = 205), frontotemporal dementia (FTD) (n = 29), mixed dementia (MXD) (n = 39) and dementia with Lewy bodies (DLB) (n = 23) were included. All patients underwent a neuropsychological examination and behavioural assessment by means of a battery of scales (Middelheim Frontality Score (MFS), Behave‐AD, Cohen‐Mansfield Agitation Inventory, Cornell Scale for Depression in Dementia). Results In AD and MXD, activity disturbances and aggressiveness occurred in more than 80% of the patients. With a prevalence of 70%, apathy was very common whereas delusions and hallucinations were rare in FTD patients. Frequently used behavioural assessment scales like the Behave‐AD systematically underestimated BPSD in FTD whereas the MFS displayed high sensitivity for frontal lobe symptoms. Hallucinations discriminated DLB patients from other dementias. A high prevalence of disinhibition (65%) in DLB pointed to frontal lobe involvement. Conclusions Behavioural assessment may help differentiating between different forms of dementia, further stressing the need for the development of new and more sensitive behavioural assessment scales. By means of the MFS, frontal lobe involvement was frequently observed in DLB. As 70% of FTD patients displayed apathy, prevalence was about two times higher compared to the other disease groups, meanwhile indicating that apathy is frequently observed in dementia, irrespective of its etiology. Copyright © 2005 John Wiley & Sons, Ltd.