Background: SNAP-IV rating scale developed by Swanson, Nolan and Pelham to diagnose Attention Deficit Hyperactivity Disorder (ADHD). The aim of this study was determination of psychometrics specifications of this scale. Methods: This was a methodological, applied and validity assessment study. One thousand students at 7 to 12 years of age in primary school in Tehran city were selected by cluster sampling. Then the students' teachers were asked to complete rating scale to consider behavior of their student. Thirty staff members of sample group were retested with SNAP-IV and was interviewed with DSM-IV. Data were analyzed by factor analysis, Pearson correlation coefficient, Kolmogrov-Smirnov and Behrens-Fisher t tests. Findings: Criterion validity was 55%. Factor analysis was detected 2 factors that explain 71% of the total variance. Reliability coefficient by test-retest was 88%, internal consistency coefficient was 95%, and Split-half coefficient was 73%. Cut-off point in scale and subscale was 2.08, 2.10, and 2.37 respectively. Conclusion: The SNAP-IV rating scales have fit psychometrics characters. Therefore, it is useable in screen study and therapeutic conditioning. Key words: Rating scale, Attention deficit-hyperactivity disorder, Reliability, Validity, Cut-off point.