A sample of 30 subjects, 10 ADHD and 20 non-ADHD children, statistically controlled by age, gender, school grades and normal full scale intelligence quotient, was selected. A test of math problem solution ability, containing four problems for each grade, with verbal and numerical irrelevant content; to measure cognitive inhibitory control was administered. ADHD children exhibited significantly inferior performance on choosing correct answers (p: 0.011) with a large effect size (d: 1.00) and a significantly superior number of irrelevant answers (p: 0.004) with a very large effect size. In conclusion ADHD children showed a cognitive inhibitory control disorder, measured with MPS