The Conners’ Rating Scales are widely used to assess attention deficit/hyperactivity disorder (ADHD) and related difficulties in children and adolescents. A short form of the scales is available, which, along with the several advantages of brief versions, also displays good psychometric properties. Nonetheless, no studies have confirmed them in cultural contexts different from the original one. The present study examined the psychometric properties of the Self-Report, Parent, and Teacher Conners 3–Short Forms in terms of reliability and validity in an Italian sample. Analyses were performed on 591 children and adolescents, 631 parents’ ratings, and 325 teachers’ ratings. To test for discriminative validity, ADHD clinical samples of 55 youth, 63 parents, and 15 teachers were compared to gender- and age-matched groups. Findings confirmed the original multidimensional structures and supported the Conners 3–Short Form scales as reliable and valid tools to assess ADHD and its main comorbid conditions.