Montreal Cognitive Assessment (MoCA) is a new cognitive tool developed for screening mild cognitive impairment (MCI). The authors examined validity of MoCA and discriminating power of subtests in a Turkish population comprising of 474 participants (246 healthy controls, 114 subjects with MCI and 114 subjects with dementia). The ANCOVAs showed that age and education had a main effect on MoCA scores. Cut scores were computed according to different education levels. The overall cut-off values for MCI and dementia were found to be lower compared to western studies. MoCA was found to have good internal consistency. The subtests most useful in discriminating MCI from healthy controls were recall, visuospatial and language, while in discriminating dementia from MCI were visuospatial, orientation and attention subtests. The results demonstrated that MoCA is a valid and reliable instrument in screening MCI, and compared with the MMSE, MoCA was proved to have superior sensitivity and specificity in detecting MCI.