We evaluated the cognitive impairment of two patients with genetically confirmed spinocerebellar ataxia type 2 (SCA2). Neurological examination revealed ignorance of his illness and Gegenhalten phenomenon in patient 1, and emotional incontinence in patient 2. Although their mental status evaluated by HDS-R or Mini-Mental State Examination (MMSE) was almost normal, the results of WAIS-R and Wisconsin Card Sorting Test (WCST) revealed the existence of intellectual decline and executive dysfunction. 3D-SSP SPECT demonstrated distinct hypoperfusion in bilateral frontal lobes, whereas brain MRI revealed no apparent cerebral atrophy in both patients. These results raise the possibility that frontal lobe dysfunction was observed in the early stages of SCA2, and that 3D-SSP SPECT is useful for evaluating the involvement of frontal lobe dysfunction in SCA2.