BACKGROUND: We analyzed the performance on a naming test and the correlations between the scores on the naming test and neuropsychological test scores in patients with mild cognitive impairment (MCI) and mild Alzheimer's disease (AD). METHODS: The subjects included 69 patients with MCI and 33 patients with mild AD. We performed general cognitive functions, the Korean version of the Boston Naming Test (K-BNT), the digit span test, the Rey figure copy test (RCFT), the Seoul Verbal Learning Test (SVLT), and frontal function tests. The detailed items of the K-BNT were analyzed for the two subject groups, and the correlations between the K-BNT scores and those of the neuropsychological tests were examined. RESULTS: Significant differences were observed on the item for the number of correct answers after two syllables on the K-BNT task in patients with AD and MCI (p<0.05). A qualitative analysis of the incorrect K-BNT responses showed that both the AD and MCI groups made semantic errors more than visuoperceptual and phonemic errors. Significant correlations were found among the Mini-Mental State Examination, the Global Deterioration Scale, clinical dementia rating, digit span, SVLT delayed recall, RCFT and RCFT delayed recall, and the Stroop test color reading items (p<0.01). CONCLUSION: Our result suggests that semantic errors gradually increase with the progress of cognitive disability in the state preceding AD among patients with MCI.