Background and Objectives: Researches on attention deficit and hyperactivity disorder indicated that this common disorder would not be resolved with age and continues into adulthood. This study was carried out with the objective of validation and normalization of diagnostic scale of adult attention deficit/hyperactivity disorder scale in Iranian sample.

Methods: This study was performed as a psychometric study on the patients (1400 to 1600 cases) referred to two psychiatry and neurology clinics in Tehran in the autumn and winter of 2014. Among these patients, 301 persons were selected by purposeful non-random sampling according to the sample size formula based on ratio or two-value variable (patient and non-patient) and related questionnaire was administered to them. Cronbach's alpha, Spearman- Brown, and Guttmann’s coefficients was used to evaluate concurrent validity and reliability and exploratory and confirmatory factor analysis in order to assess the construct validity.

Results: In this study, Cronbach's alpha of the total scale was 0.88 and for the subscales of inattention, hyperactivity, and impulsivity were 0.82, 0.72, 0.67, respectively. The correlation coefficients between the mentioned scale and adult attention deficit/hyperactivity questionnaire (Wender Utah) was obtained 0.59, and between the subscales and the Wender Utah questionnaire, were 0.56, 0.49, and 0.40, respectively, which all three were significant (p<0/01). Confirmatory factor analysis results showed that this scale has three factors and two goodness-of-fit indices.

Conclusion: The results of this study revealed that specialists can diagnose and treat the patients using this diagnostic scale.