Voluntarily directing visual attention to a cued position in space leads to improved processing of forthcoming visual stimuli at this position, due to anticipatory tuning of visual cortex activity. Recent evidence points to a determining role of modulations of posterior alpha-band activity (8-14Hz) during attention orienting.This thesis investigates the modulation of EEG alpha-oscillations during anticipatory preparation for a visual target. The results show that the topography of alpha band power maps is found to correspond to a retinotopic organisation according to the direction of attention in the time prior to the expected target arrival. Moreover, the thesis presents evidence for a dynamic modulation of alpha amplitudes according to task demands by showing that both alpha power decreases and increases can occur at different times in the course of anticipation of a visual target stimulus. The findings presented here provide further support for an active facilitative versus inhibitory role of alpha-power decreases and increases during attention orienting, by showing retionotopic specificity and dynamic deployment of attentional resources to prepare versus maintain the cortex for optimal target processing.