Teachers' perceptions of attention deficit hyperactivity disorder (ADHD) can influence the diagnostic rates of the disorder and the management of children in schools. This study investigated the knowledge and perceptions of ADHD in a sample of 589 Italian primary school teachers using a self-report questionnaire that included the ADHD perceptions questionnaire (Norvilitis & Fang, 2005) and the ADHD knowledge scale (Jerome, Gordon, & Hustler, 1994). The results showed that Italian teachers had a moderate level of knowledge, that their perceptions of ADHD were ambivalent, that their teaching experience was not positively correlated with their perceptions and knowledge of ADHD, and that receiving specialized information about ADHD had a limited influence on their perceptions. These findings suggest that perceptions are more than a matter of knowledge and should be addressed with regard to deep cultural values and representations. The educational and psychological implications of these results are discussed; particular attention is given to the importance of understanding the social context of ADHD and taking into consideration the teachers' perceptions of ADHD in the organization of training. Future research should address the role of children's gender in influencing perceptions of ADHD as well as the perceptions of parents and siblings.