This study examined the relationship between the developmental trajectories of neuropsychological functioning and ADHD symptomatology in a longitudinal sample of children ages 9 to 14. Participants and measures were derived from the Multimodal Treatment Study for ADHD including 534MTA participants and 254 normal controls. Despite improvement over time, MTA participants continued to receive higher ratings of ADHD symptomatology and exhibit greater difficulties across the majority of neuropsychological outcomes. No relations were found between improvements in neuropsychological functioning and ADHD symptomatology over time. Findings provide support for the persistence of neuropsychological functioning and ADHD symptomatology. Findings did not support the hypothesized relation between improvements in frontally-mediated neuropsychological functioning and ADHD symptomatology possibly due to the brief 1-year lag and limited assessment battery. Findings are discussed in relation to neuropsychological development including recommendations for future research.