Selective attention allows people to process some stimuli more thoroughly than others. This is partly under voluntary control, and partly determined by stimulus salience. Selective attention has been studied with psychological methods for many years, but recent cognitive neuroscience studies using brain-imaging methods (and other neurobiological measures) have transformed the topic. Such studies have demonstrated that sensory processing can be strongly modulated by attention throughout perceptual networks, including even processing in primary sensory cortex. They have shown that some of these modulations can be anticipatory, arising prior to stimulus presentation, while other components reflect a changed neural response to an incoming stimulus. Recent imaging studies have also examined the mechanisms involved in controlling such attentional modulation of sensory processing. In addition to answering many long-standing questions about selective attention, such research also raises new questions. The various contributions in this volume provide an overview of the spectacular recent advances in attention research using neurobiological measures, and they outline critical issues to be resolved in the future.