Attention-Deficit/Hyperactivity Disorder (ADHD) is a common childhood disorder affecting approximately 5% of primary school-aged children. The disorder is characterised by severe difficulties in one or more of three areas; inattention, impulsivity, and hyperactivity. Considering that primary school teachers are often the first to notice behavioural difficulties in children, it is surprising that relatively little research has been undertaken with teachers. The limited research that has been conducted on teachers’ knowledge has shown that knowledge scores range from 50 to 70%, and most attitudinal research has merely assessed knowledge. There is also a dearth of research assessing teachers’ classroom management of children with ADHD, and very little emphasis has been placed on research within a theoretical context. This paper details a study aimed at understanding the links between teachers’ knowledge, attitudes and behaviour using two social psychological theories: Theories of Reasoned Action (TRA) and Planned Behaviour (TPB).