Objective: Etiological models of attention-deficit hyperactivity disorder (ADHD) increasingly support the role of a motivational dysfunction pathway, particularly for hyperactive-impulsive symptoms. Overactive behavioral approach tendencies are implicated among these motivational accounts. However, other externalizing disorder symptoms, such as the psychopathy dimension, are also associated with behavioral approach and frequently co-occur with ADHD. The current study tested the hypothesis that behavioral approach is differentially associated with hyperactive-impulsive ADHD and psychopathy symptoms. Method: A sample of young adults (n = 220) completed self-report measures assessing behavioral approach and inhibition, ADHD symptoms, and psychopathy symptoms. Results: Structural equation analyses supported the hypothesis that behavioral approach predicts hyperactive-impulsive ADHD symptoms while considering symptom overlap with psychopathy symptoms. Conclusion: These findings support motivational accounts that behavioral approach tendencies are predictive of ADHD symptoms and address concerns about externalizing comorbidity. Implications for ADHD etiology are discussed. (Contains 6 notes, 2 tables, and 1 figure.)