This study investigated the effects of response rate and attention focusing on performance of ADHD, clinical-control (CRNA) and non-clinical control children in response inhibition tasks. All children completed the "Go-NoGo" task, a computer-based task of attention and impulsivity. Focused attention on this task was manipulated using a priming arrow, and reaction time and accuracy served as dependent variables. Results indicated that children with ADHD and children in the CRNA group performed more poorly than children in the Control group. Results failed to support the assertion that state regulation or inhibition is a unique deficit in children with ADHD. Evidence was found to suggest that clinical samples have difficulty with response regulation and visual orienting skills. The presence of cognitive deficits in all clinical group children suggests that more research is needed to more clearly delineate differences between childhood psychopathologies and that treatments for cognitive deficits should benefit various groups of children including but not limited to those with ADHD. (Contains 2 tables and 6 figures.)