The objective of this study was to find changes in EEG power during emotions of positive, negative valence as compared with neutral condition, evoked by the International Affective Pictures. The subjects were 36 young, healthy male university students.  Power values were calculated from 21 referential derivations. Statistical analyses were carried out with Repeated ANOVA Measures having 3 conditions (positive, negative and neutral picture presentations), four bands and the above mentioned 21 leads) . Fisher´s LSD post hoc test revealed the topography of the significant differences. The objective of the study was to see whether right hemisphere is preferential for emotions or there is a hemispheric frontal alpha decrease according to the valence of the emotions. Our results show that most differences between emotional conditions occurred in the delta and theta bands band at frontopolar, frontal, temporal, parietal and occipital leads, without preference for right hemisphere participation. Right, left and midline leads both show significant differences between emotional conditions.  In the alpha and beta bands very few significant differences between emotional states were observed, none of them at frontal areas. Alpha and beta activity revealed only negligible differences between pleasant and unpleasant conditions and the areas where activation occurred had no relation with the valence of the stimuli. The results obtained for relative power (RP) values were significant only in the delta band. Based on our results we can conclude that data do not show a defined pattern of activity, but various areas and both hemispheres respond to emotions. These findings are in accordance with previous reports of FMRI studies.