Clinical discrimination of the early stages of AD and MCI is challenging. MRI indices which are simple enough to be applied by non-radiologists on hard copies would be of practical importance in the discrimination. We studied 45 consecutive patients (17 with MCI, 25 with AD, 3 with normal cognitive findings) with at least one white matter lesion (WML) on axial fluid-attenuated inversion recovery (FLAIR) MRI sequences. WML load was evaluated by Fazekas' scoring system; temporal lobe atrophy by interuncal distance (IUD) measurement. WML pattern had no significant discriminative value of AD and MCI. No significant correlation between periventricular/subcortical WML scores and neuropsychological test results was observed. The mean IUD was significantly smaller in patients with MCI compared to those with AD. The cut-off value of IUD was 28.3 mm with receiver operating curve (ROC) analysis. Area under the curve was 0.925 (95% CI: 0.800-0.983). A significant negative correlation between IUD and the mini mental state examination (MMSE), verbal fluency, clock drawing, and Rey Auditory verbal learning test (AVLT) was noted. The results indicate that measurement of IUD is a clinically useful test in discrimination of AD and MCI patients with WML(s) on brain MRI. However, severity of these lesions is not useful for distinctions. (c) 2006 Elsevier Ireland Ltd. All rights reserved.