The Dementia with Lewy Bodies (DLB) Consortium refined its recommendations for the clinical diagnosis of DLB last year. The generalized low uptake of single photon emission computed tomography (SPECT)/positron emission tomography (PET) perfusion/metabolism scan with reduced occipital activity with or without the cingulate island sign (CIS) in FDG-PET imaging was described as a supportive biomarker of DLB. CIS shows that brain metabolism in the posterior cingulate of patients with DLB is relatively preserved compared with Alzheimer's disease (AD). Metabolism in the posterior cingulate is known to be dicreased in patients with AD. CIS is also known to have negative correlation with the Braak neurofibrillary tangle stages. Recently, we studied CIS of brain perfusion SPECT and concluded that optimized CIS using brain perfusion SPECT is clinically useful for differentiating DLB from AD. This feasibility of studying CIS using brain perfusion SPECT when diagnosing DLB is described in this article.