Objective To investigate relations between EEG measures and performance on tests of global cognition, memory, language and executive functioning. Methods Twenty-two controls, 18 patients with mild cognitive impairment (MCI) and 16 with probable Alzheimer’s disease (AD) underwent neuropsychological and EEG investigations. We used the following EEG measures: theta relative power during eyes closed, alpha reactivity during memory activation (i.e. the percentual decrease in alpha power as compared to eyes closed) and alpha coherence during eyes closed and memory activation. Results Theta relative power was increased in AD patients as compared with controls (p <0.001) and MCI patients (p <0.01) and related to decreased performance in all cognitive domains. Alpha reactivity was decreased in AD patients as compared with controls (p <0.005) and related to decreased performance on tests of global cognition, memory and executive functioning. Alpha coherence did not differ between groups and was unrelated to cognition. Conclusions EEG power measures were associated with decreased performance on tests of global cognition, memory, language and executive functioning, while coherence measures were not. Significance The EEG yielded several power measures related to cognitive functions. These EEG power measures might prove useful in prospective studies aimed at predicting longitudinal cognitive decline and dementia.