Objective: Cognitive impairment has been an area of interest for psychiatrists. Not only do patients with dementia exhibit symptoms associated with cognitive impairment, but those with some mental disorders such as psychotic and mood disorders as well. However, differences in cognitive impairment between these disorders remain unclear. In this study, we used the Korean Mini-Mental State Examination (K-MMSE), a tool that can be easily administered to patients, to compare cognitive impairment profiles among patients with dementia, psychotic disorders, and mood disorders. Methods: We collected demographic and clinical characteristics of 59 patients who were over 50 years old. Cognitive func-tion was assessed using the K-MMSE. Patients were divided into three groups based on International Classification of Diseases 10th revision diagnosis codes: 1) F00-F01 Dementia, 2) F20-F29 Psychotic disorders, and 3) F30-F39 Mood disorders. We compared K-MMSE subscale scores between the three groups using one-way analysis of variance. Results: The three groups did not differ in demographic data. The dementia group showed the lowest scores in orientation to time (standard deviation [SD]=1.45, F=3.233, p<0.05) and place (SD=1.25, F=3.388, p<0.05), as well as registration (SD=1.00, F=4.425, p<0.05) and recall (SD=0.91, F=3.364, p<0.05) of memory compared to the groups with psychotic and mood disorders. The psychotic disorder group showed significant impairment in language (SD=1.34, F=3.348, p<0.05) compared to the other groups. No significant differences were observed in calculation and drawing. Conclusion This study suggests that certain K-MMSE subscale scores could indicate an illness that causes cognitive impairment, especially in dementia, psychotic disorders, and mood disorders. By using K-MMSE profiles, we could provide better in-terventions for patients with cognitive impairment.