Background: Deficits in executive functioning are supposed to have a predisposing influence on impulsive or aggressive behaviour. We tested the hypothesis that oppositional-defiant disorder (ODD) children with or without attention deficit hyperactivity disorder (ADHD) have problems in executive functioning. Method: Seventy-seven 7- to 12-year-old children (15 ODD, 26 ODD/ADHD, and 36 normal controls), all with normal IQ, completed 7 neuropsychological measures of executive functioning, assessing the abilities of set shifting, planning, working memory, inhibition/attention, and impulsivity. Some of these tasks involved the possibility of monetary rewards with a view to testing the prediction of a specific motivational inhibitory deficit. Results: We found no evidence of deficits in working memory, planning, inhibition, or impulsivity. However, the ODD/ADHD group was worse than the normal control (NC) group in set shifting, and both the ODD and ODD/ADHD groups performed worse on a response perseveration task. Moreover, on the basis of one variable derived from a motivational inhibition task, 77% of the children could be correctly classified as ODD or NC. Conclusions: The findings do not support the hypothesis that ODD and ODD/ADHD children have a deficit in executive inhibitory control; rather, they emphasise that they have problems in regulating their behaviour under motivational inhibitory conditions.