Abstract: Objective To investigate the differences of the ability to monitor and resolve the conflicts among children with attention deficit hyperactivity disorder (ADHD), ADHD comorbid oppositional defiant disorder (ODD), and normal children. Methods Event related potentials (ERP) were recorded in fifteen children with ADHD, 18 children with ADHD comorbid ODD, and 18 normal children. Results ERP results showed that the “Go” stimulation time were significantly longer and the correct rates were significantly lower in ADHD group and ADHD comorbid ODD group than those in control group. There were no differences in “Nogo” stimulation time and correct rate among ADHD group, ADHD comorbid ODD group and control group. Latency periods of Go-N2 and Nogo-N2 were significantly longer in ADHD group and ADHD comorbid ODD group than those in control group. However, there was no difference between ADHD group and ADHD comorbid ODD group. Amplitudes of Nogo-P3b were significantly smaller in ADHD group and ADHD comorbid ODD group than those in control group. There was no difference between ADHD group and ADHD comorbid ODD group. Conclusion In children with ADHD, the ability of conflict monitoring was delayed and the ability of conflict resolving was diminished, especially in the second half procession of conflict.