BACKGROUND: Frontotemporal dementia (FTD) has a characteristic pattern of lobar atrophy in frontal and/or temporal lobes. Asymmetry in the lateral ventricle size on brain magnetic resonance image (MRI) in FTD patients may have clinical significance. This study compares the ventricular asymmetry seen on MRI with that of the neuropsychological difference and asymmetric hypoperfusion using statistical parametric mapping (SPM) analysis of brain SPECT in patients with FTD. METHODS: Thirteen FTD patients who underwent Brain MRI, TC-99m ECD SPECT and neuropsychological testing and who had the ventricular asymmetry on brain MRI were retrospectively selected. The patients were divided into two groups (5 right dominant group, 8 left dominant group) according to the ventricular asymmetry on brain MRI. We compared the regional blood flow pattern on TC-99m ECD SPECT images using SPM analysis and the results of neuropsychological tests between the two groups. RESULTS: In the right dominant group, a significant perfusion deficit was identified at the bilateral frontal regions. In the left dominant group, significant hypoperfusion was found at the left frontotemporal regions (uncorrected p<0.001). There was no significant difference of neuropsychological testing in between the two groups. However, the score on the Neuropsychiatric Inventory (NPI) in the right dominant group was higher than that of the left dominant group (p=0.043). CONCLUSIONS: Hemispheric asymmetry on brain MRI was common in patients with FTD and was related with a characteristic pattern of hypoperfusion on brain SPECT images and neuropsychiatric symptoms.