Working memory and behavioral inhibition have been identified as potential underlying deficits of attention-deficit/hyperactivity disorder (ADHD) in competing models of the disorder. The stop-signal (SS) paradigm is often reified as a measure of behavioral inhibition across ADHD research. However, the choice reaction time component of the SS task likely places demands on working memory processes, consequently confounding the paradigm as a pure measure of inhibition. Therefore, the current study examined the relationship between multiple inhibition tasks to test competing models of ADHD. Forty-six boys, between 8 to 12 years old, with and without ADHD, were administered working memory (phonological and visuospatial tasks) and behavioral inhibition (go/no-go and SS) tasks. Bias-corrected bootstrapped mediation analyses indicated that working memory accounted for the relationship between group membership (ADHD and typically developing children) and both measures of inhibition. In contrast, only SS inhibition mediated the relationship between group and working memory. Overall, these findings suggest that studies that use the SS paradigm may be confounded by controlled-focused attention associated with the choice-reaction time element of the stop-signal task. Additional research that utilizes alternative measures of behavioral inhibition is needed to determine the extent of the overlap in children with the disorder.