Background Several instruments are available to measure cognitive functioning in older adults. However, there is paucity of information about their factorial structure and psychometric properties. Aim To determine the factorial structure and the internal reliability of the Mini Mental State Examination (MMSE), the Montreal Cognitive Assessment (MoCA) and the Adenbrookke´s Cognitive Examination (ACE-R), and their cognitive impairment detection capabilities. Material and Methods MMSE, MoCA and ACE-R were applied to 203 older adults aged 54 to 88 years (77% women), excluding participants with dementia. Results The factorial structure of the MMSE suggested that items referred to memory process should be eliminated due to their low reliability and factor loading (b = 0.12; p = 0.146). Although the MoCA had a good reliability, object denomination process items also had to be dropped (b = 0.22; p = 0.003). The ACE-R demonstrated a single factorial structure for all cognitive processes and had a good internal consistency. MMSE, MoCA and ACE-R classified as having dementia 5, 27 and 42% of participants, respectively. Conclusions MoCA and the ACE-R scales appear as better instruments to detect dementia in older people.