PURPOSE: This study aims to evaluate the incidental findings on brain MRI of patients with cognitive function impairments. MATERIALS AND METHODS: We analyzed magnetic resonance (MR) findings of 236 patients with decreased cognitive function. MR protocols include conventional T2 weighted axial images, fluid attenuated inversion recovery axial images, T1 weighted coronal 3-dimensional magnetization-prepared rapid acquisition of gradient echo and diffusion tensor images. We retrospectively evaluated the signal changes that suggest acute/subacute infarction and space occupying lesions which show mass effect. RESULTS: Incidental MR findings were seen in 16 patients. Nine patients (3.8%) showed increased signal intensity on trace map of diffusion tensor images suggesting acute/subacute infarctions. Space occupying lesions were detected in 7 patients, and 3 lesions (1.27%) had mass effect and edema and were considered clinically significant lesions that diminish cognitive functions. CONCLUSION: Several incidental MR findings were detected in patients with decreased cognitive function, and the incidence of aucte/subacute infarctions were higher. Proper evaluations of MRI in patients with impaired cognitive functions will be helpful in early detection and management of ischemic lesions and space occupying lesions.