Objective The aim of this study is to investigate whether a combination of the Korean version of the mini-mental state examination (K-MMSE) and the Korean dementia screening questionnaire (KDSQ) is better than the use of test alone when differentiating patients with dementia from those without dementia in Korea. Methods The subjects (patients without dementia, 1120; patients with dementia, 908) were recruited from the Clinical Research Center for Dementia of South Korea. K-MMSE and KDSQ were used. Diagnosis of dementia was made according to the Diagnostic and Statistical Manual of Mental Disorders, fourth Edition. The weighted sum rule derived from logistic regression analysis was used for the combination of K-MMSE and KDSQ. Results On comparing the Area Under the Curve for each test using the method of Hanley and McNeil, the weighted sum was significantly greater than KDSQ or K-MMSE, and K-MMSE was significantly greater than KDSQ. Conclusion This study shows that when differentiating patients with dementia from those without dementia in Korea, a combination of K-MMSE and KDSQ achieved using the weighted sum method is better than either test performed alone. Further epidemiological studies in community-based settings are required before our results can be generalized to nonclinical samples.