Objective: Current diagnostic criteria specify that ADHD involves difficulties with inattention and/or hyperactivity/impulsivity. Researchers using factor analysis have consistently found support for an inattention factor in both children and adults. Findings have been mixed regarding whether hyperactivity and impulsivity reflect one or two dimensions. To date, no study has examined the merits of separating hyperactivity and impulsivity factors to predict socioemotional and academic outcomes in young adults. Method: The current study examined self-reported ADHD symptomatology data from 1,096 college students. Subsets of the sample completed a variety of outcome measures. Results: The prediction of outcomes provided support that complemented confirmatory factor analysis for the separation of the hyperactivity and impulsivity constructs. Impulsivity uniquely predicted more outcomes than hyperactivity alone. Conclusion: Results were consistent with the conceptualization of ADHD as primarily a disorder of behavioral inhibition. Future research using alternative outcomes and clinical populations should be conducted. (Contains 2 tables.)