OBJECTIVES: Donepezil is a widely used drug for the treatment of patients with Alzheimer's disease(AD). The aim of the present study was to clarify the efficacy and the characteristics of responders to donepezil. METHODS: Patients with probable AD(n=80 ; 75.7 years) and small vessel dementia(SVD)(n=18 ; 77.8 years) who received donepezil were retrospectively analyzed using Alzheimer's registry, and three questions were asked: 1) Does donepezil therapy improves cognitive symptoms in patients with dementia? 2) If donepezil improves cognitive symptoms, which items of the K-MMSE are improved? 3) What are the characteristics of responder to donepezil medication? RESULTS: 1) After donepezil medication, cognitive function measured by the K-MMSE was significantly improved in both types of dementia(AD and SVD), However, statistical differences were not found between these groups. 2) In a clinical trial of donepezil, the patients performed better than before mediation on K-MMSE items assessing orientation, recall, construction, concentration, calculation. 3) In AD, the K-MMSE score before medication was closely related with response of donepezil. CONCLUSION: This study suggests that donepezil improves various cognitive functions in both types of dementia, and the responsive group had significantly lower K-MMSE scores than the non-responsive group before medication.