The investigation of ADHD prevalence in kindergarten children in northeast Iran and a determination of the criterion validity of Conners' questionnaire via clinical interview

► The prevalence of ADHD in kindergarten children in northeast Iran was estimated at 12.3% ± 2.12%. ► The prevalence of ADHD was 18.1% in boys and 6.7% in girls; this gender difference is significant (P < 0.0001, Z = 5.75). ► Conners' parent-teacher questionnaire can be a suitable method for the primary screening of children for ADHD. The sensitivity and specificity of questionnaire were estimated to be 90.3% and 81.2%, respectively. ► The predictive criterion validity of the questionnaire was estimated to be 90.3%.