Since the publication of DSM-IV (1994) the diagnostic criterions of Attention Deficit/ Hyperactivity Disorder (ADHD) have been changed, but, in Italy, a scale has not yet been created yet for the evaluation of troubling behaviour of children with ADHD. With the SDAI Scale, intended for teachers, it's possible to assess the presence of ADHD symptoms according to DSM-IV items and to obtain a quantitative evaluation about the severity of the problem. The SDAI Scale shows good psychometric properties and it offers information about the epidemiology of ADHD. Data was collected in primary schools in the province of Ferrara, with a sample of 973 children aged 7 to 10. According to teacher evaluations children with ADHD-subtype inattentive are 6%, those with ADHD-subtype hyperactive-impulsive are 0.7% and those ones with ADHD-subtype combined are 1.5% of the sample considered.