Anxiety disorder (ANX) is characterized by heightened arousal, psychosocial and academic difficulties, and comorbidity with other disorders, in particular, attention-deficit/hyperactivity disorder (ADHD). The heightened arousal contributes to cognitive impairment by adversely affecting executive control of cognition. The nature of the effect on executive control is poorly understood. Research in this area could inform intervention, diagnostic, and etiological research. Our objective was to characterize children with ANX on measures of executive functioning, while controlling for comorbid ADHD. We compared children ages 6-14 with ANX (N=21), ADHD (N=78), ANX+ADHD (N=38), and normal controls (NC; N=40) on the stop task, a measure of performance monitoring and response inhibition. No difference was observed between NC and ANX groups in performance monitoring. Compared to the NC group, the three clinical groups showed inhibition deficits, and both ADHD and ANX+ADHD groups monitored less after responses. ANX was not associated with performance monitoring or inhibition deficits once comorbid ADHD was considered. This emphasizes the importance of controlling for comorbid ADHD in studies of cognition and anxiety.