Adolescents with ADHD have a greater lifetime history of concussion and experience concussion-like symptoms in the absence of a concussion, complicating concussion assessment and management. It is well established that individuals who experience greater acute symptoms following concussion are at risk for slower recovery and persistent symptoms. We examined whether youth with ADHD experience worse acute effects, within the first 72 h following concussion, compared to youth without ADHD. We hypothesized that youth with ADHD would perform worse on neurocognitive testing and endorse more severe symptoms acutely following injury, but the magnitude of change from pre injury to post injury would be similar for both groups, and thus comparable to baseline group differences. The sample included 852 adolescents with pre-injury and post-injury ImPACT results (within 72 h); we also conducted supplementary case-control analyses on a subset of youth with and without ADHD matched on demographics and pre-injury health history. For both samples, there were significant interaction effects for the Verbal Memory and Visual Motor Speed composites (p < 0.01, eta(2)=.01-.07, small-medium effect), such that youth with ADHD showed a greater magnitude of diminished cognitive functioning from pre-injury to post-injury testing. There were no significant differences in the magnitudes of changes from pre injury to post injury with regard to overall symptom reporting (i.e., total symptom severity scores, total number of symptoms endorsed); however, there were group differences in endorsement rates for several individual symptoms. Further research is needed to determine whether such differential acute effects are associated with recovery time in youth with ADHD.