BACKGROUND AND PURPOSE: We investigated dementia in patients with multiple system atrophy (MSA) in order to characterize the prevalence and nature of impairments in these patients.  METHODS: Fifty-eight MSA patients were recruited in our institution between April 1996 and December 2006 and investigated.  RESULTS: Of 58 patients, 10 were diagnosed with dementia.  There were no significant differences in age at onset, gender, duration of disease, or severity of cerebellar dysfunction between patients with and without dementia.  The early and delayed heart to mediastinum (H/M) ratios obtained with (123)I-metaidobenylguanidine (MIBG) cardiac scintigraphy were significantly decreased in patients with dementia compared with those without dementia.  Of the 10 patients with dementia, three were found to have cognitive decline that preceded onset of motor symptoms.  White matter lesions were evident in these patients, whilst frontal atrophy was prominent in patients whose cognitive decline was preceded by onset of motor symptoms.  CONCLUSIONS: Dementia in patients with MSA may be more common than previously thought, furthermore, we speculate that clinical features of dementia in these patients might be heterogeneous.