The study examined performance of 6- to 11-year-old children, from gifted and mainstream academic programs, on measures of mental-attentional capacity, cognitive inhibition, and speed of processing. In comparison with mainstream peers, gifted children scored higher on measures of mental-attentional capacity, responded more quickly on speeded tasks of varying complexity, and were better able to resist interference in tasks requiring effortful inhibition. There was no group difference on a task requiring automatic inhibition. Comparisons between older and younger children yielded similar results. Correlations between inhibition tasks suggest that inhibition is multidimensional in nature, and its application may be affected by task demands. Measures of efficiency of inhibition and speed of processing did not explain age or group differences on a complex intellective measure of mental-attentional capacity.