Aim of the study is to discriminate among participants with mild cognitive impairment through electroencephalography brain rhythms. A total of 79 participants with MCI were classified into 4 subgroups based on the beginning of memory complaints up to the time of first visit. All participants underwent electroencephalography recording, magnetic resonance imaging, apolipoprotein E characterization, and volumetric morphometry estimation of hippocampal region. Electroencephalography markers show 2 distinct patterns: (1) increase of theta/ delta power ratio and highest value of alpha2 band power in the group with shorter duration of disease, the greater right-left hippocampal volume difference and worst memory performance; (2) the highest value of alpha3 band power and the highest alpha3/alpha2 power ratio in the group with the lesser total hippocampal volume but preserved memory performance. Apolipoprotein E4 is linked to a major risk of early beginning of disease. Electroencephalography markers allow a mean correct percentage of correct classification up to 89%.