Attention deficit hyperactivity disorder (ADHD) diagnosis rates have increased significantly in recent times. A teacher's role is crucial in determining if a child will be referred for an ADHD assessment. Teachers' opinions and observations are also required for and play a huge role in the actual assessment process. For this reason, their knowledge of ADHD is also an important part of this process. This research has measured, on a small scale, Irish primary schoolteacher's knowledge and conceptions about ADHD using the Knowledge of Attention Deficit Disorders Scale (KADDS) questionnaire. Ninety teachers participated in the research from 11 primary schools in County Clare. A quantitative method was utilised enabling the research to be comparable with other pieces of research using the same questionnaire. Data in relation to the teachers' professional background were also gathered in order to analyse significant differences based on a variety of factors. The results were analysed as prescribed in KADDS test manual using the statistical software package SPSS. This research shows that Irish primary schoolteachers are more knowledgeable in regards to ADHD symptoms and diagnosis than they are in the areas of associated features or treatments. It also shows that knowledge levels of Irish primary schoolteachers are higher than teachers in earlier research using the same questionnaire.