To assess noun and verb processing in different dementia types, we tested object and action naming in three groups of subjects: probable Alzheimer's disease (AD) with mild to moderate dementia; age- and education-matched normal subjects; and a group of frontotemporal dementia (FTD) patients. AD and FTD patients were impaired in naming compared with control subjects; action naming was more severely impaired. However, the discrepancy between object and action naming was significantly greater in FTD than in AD patients, independent of the severity of dementia or of overall language impairment. The latter finding is compatible with the hypothesis that the frontal lobe plays a crucial role in action naming. A relatively selective impairment in action naming might be a characteristic neuropsychological feature of FTD.