The effect of atomoxetine (ATX) on executive function has been assessed by means of questionnaires only. The aim of this study was therefore to evaluate the efficacy of ATX using standard variables of a computer-based continuous performance test (cb-CPT) combined with an infra-red motion-tracking device at different times of the day. One hundred twenty-eight girls and boys aged 6 to 12 years with a diagnosis of ADHD according to DSM-IV-TR criteria were randomized in the study. The primary efficacy measures were the q-scores of the cb-CPT combined with an infra-red motion-tracking device. The test comprises 13 neuropsychological variables that can be taken to reflect hyperactivity, inattention, or impulsivity. One hundred five patients completed the study (ATX group: n=54; placebo group: n=51). ATX (target dose 1.2 mg/kg/day) over 8 weeks was significantly superior to placebo in reducing hyperactivity, inattention, and impulsivity as measured by q-scores of 10 primary variables of the cb-CPT. Both groups of patients showed a circadian pattern of neuropsychological outcomes across the day as reflected by the cb-CPT combined with an infra-red motion-tracking device. In summary, this study demonstrated a positive effect of ATX on some aspects of executive function, inhibitory control, and hyperactivity compared with placebo.