This paper tries to define attention and hyperactivity disorder, which is in scientific literature known as ADHD (Attention Deficit and Hyperactivity Disorder). This disorder is considered to be one of the most commonly diagnosed disorders among children and adolescents. The symptoms that occur are attention deficit, impulsiveness and hyperactivity. The paper theoretically describes possible causes, symptoms, diagnostics, methods of treatment, professional competencies of preschool teachers, as well as partnership between teachers, parents and other competent participants. In the following part of the paper, study of a boy with diagnosed ADHD is shown. Case study consists of the research which was done through continual observation of the child with ADHD in his kindergarten group and noting the information about his behaviour. The way the child acts when interacting and communicating with other children and preschool teachers, his way of participating in activities is described. Among that, his preschool teachers gave their opinion about their work in the preschool group and their professional competencies to work with children with ADHD. This paper wants to show the ways the ADHD diagnosed child functions in some situations, how he is perceived by his environment and people who surround him, as well as how they react to his behaviour. The difficulties that preschool teachers and parents are faced with in their everyday life is also described.