EEG activity of 20 female volunteers was monopolarly recorded at P3, P4, C3 and C4 during four resting periods and three series of cognitive tasks: one analytic, one spatial and one demanding analytical and spatial processing or mixed task. Relative power and inter and intrahemispheric correlations were analysed. Beta relative power was significantly higher during the resting periods at the right parietal and the same pattern of asymmetry was maintained during the three series of tasks. Alpha relative power decreased and theta increased during the three series of tasks regardless of their cognitive nature as compared to baseline. Interhemispheric correlation for theta frequencies, and intrahemispheric correlation for the full band were significantly different during task solution. There were no significant differences between left and right intrahemispheric correlations.