A group of 314 Spanish-speaking elders were classified in 55 participants with mild to moderate dementia, 74 participants with mild cognitive impairment (MCI), and 185 control participants, according to clinical evaluation derived. Sensitivity, specificity, and detection characteristics of frequently cognitive and functional tests were calculated in comparison with the clinical evaluation: Minimental State Examination, Brief Neuropsychological Test Battery, Short Blessed test, Pfeffer Functional Activities Questionnaire, and Blessed Dementia Scale. Influence of education on sensitivity and specificity values varied along the tests. For all the cognitive and functional measures, a great number of MCI participants who fulfilled Mayo's (Mayo's Clinical School) clinical criteria (Petersen et al., 1999) were misclassified as controls and a few were misclassified as demented. Level of education plays a very important role in both cognitive and functional assessment. The cognitive tests that are commonly used to screen demented patients may fail to detect MCI particularly in high-functioning individuals as well as those who are well educated.