The current study utilized laboratory tasks (Conners’ Continuous Performance Test, CPT; Behavioral Inhibition Task, BIT) to examine the relationships among motivation, executive functioning, and parent and teacher-reported attention, internalizing, and externalizing problems in a clinical sample of 132 children with or without Attention-Deficit/Hyperactivity Disorder, Combined Type (ADHD-C; 69% male, mean age = 9.88). Specificity was examined through total, unique, and interactive effects via hierarchical regression. Higher CPT scores (i.e., executive disinhibition) were related to greater externalizing problems in total and unique effect analyses, while a relationship between lower CPT scores (i.e., executive inhibition) and greater internalizing problems was found only in unique effect analyses. No significant effects were found for motivational inhibition (i.e., low BIT) or disinhibition (i.e., high BIT). ADHD-C was associated with greater attention and externalizing problems in total effect analyses, but only externalizing problems showed a significant relationship in unique effect analyses. Interactive effects were found for ADHD-C and executive functioning, as lower levels of CPT (i.e., executive inhibition) coupled with ADHD-C resulted in greater parent-reported attention problems. In addition, higher CPT scores (i.e., executive disinhibition) were associated with greater parent-reported externalizing problems in Non-ADHD-C children. Although some main effects were predicted, the interactive effects were somewhat surprising, particularly in relation to ADHD-C, executive inhibition, and parent-reported attention problems. Exploratory analyses revealed that this effect may have been due to greater internalizing problems in ADHD-C children at lower levels of CPT (i.e., executive inhibition). Results are discussed in relation to past studies and laboratory task validity.