Objective: This study was conducted to develop Korean version of Modified Mini-Mental Status (3MS) Examination and to examine it’s validity and reliability in patients with brain injuries. Method: The 3MS was administered to 24 patients with brain injuries from Jan. 1 to Apr. 30 in 2001 at two university hospitals in Korea. The instruments used for evaluating validity and reliability of 3MS were Mini-Mental Status Examination (MMSE), Neurobehavioral Cognitive Status Examination (NCSE), and Modified Barthel Index (MBI). Results: Test-retest reliability of 3MS was excellent (r=0.97), and Interitem correlation coefficients ranged from 0.49 to 1.00. The score changes between the two tests were not related with the gender, level of education, and the duration after the brain injury. When items of 3MS were compared with the items of NCSE to evaluate the construct validity, correlation coefficients ranged from 0.43 to 0.73. When the NCSE was used as a gold standard to evaluate cognitive dysfunction, optimal cutoff scores analyzed by the Receiver Operating Characteristic curves for 3MS and MMSE were 68 and 22, respectively. The sensitivity and specificity of both 3MS and MMSE were the same at 80% and 89.5%, respectively. Conclusion: This study showed that the 3MS was a valid and reliable instrument to screen cognitive dysfunction in patients with brain injuries.