Abstract In this study, we examined developmental changes in auditory selective attention using both electrophysiological (Nd, P3b) and behavioral measures while two groups of children (9- and 12-year-olds) and adults were engaged in a two-channel selective attention task. Channel was determined by frequency (1000 or 2000 Hz). Targets in one condition were shorter than the standards (duration target) and in the other were softer (intensity target). We found that the Nd onset and peak latencies for the children were significantly longer than for the adults. Nd amplitude, however, did not differ between the groups. Further, all groups evidenced P3b to attended targets but not to unattended deviants. Hits, reaction times, and false alarms to unattended deviants continued to evidence improvements through adolescence. Taken together, our data are most consistent with a model of developmental improvement in the speed and efficiency of attention allocation.