BACKGROUND AND PURPOSE Frontotemporal dementia (FTD) is the second most common neurodegenerative dementia in the young age after Alzheimer disease. Recent improvement in diagnostic assessment suggests that it is more common than previously, although with a great heterogeneity in clinical presentation. The different clinical patterns related to age of disease onset in behavioural variant FTD (bvFTD) have been fairly studied. Aim of the study was to evaluate whether age at disease onset modulate the heterogeneity of either cognitive impairment or behavioural disturbances in patients affected by bvFTD. METHODS One hundred and thirty-four patients with bvFTD entered the study. Age at onset and demographic characteristics were carefully recorded. Each patient underwent a wide neuropsychological and behavioural standardized assessment, as well as a brain SPECT perfusion imaging study. RESULTS Behavioural variant FTD were subdivided into four groups according to the age at onset. The four quartile groups did not differ for demographic characteristics and family history for dementia. Global cognitive impairment as well as analysis of the different cognitive domains and behavioural patterns were comparable. CONCLUSIONS These findings provide evidence that the clinical heterogeneity of bvFTD is not explained by age at disease onset. Further studies are needed.