Attention deficit/hyperactivity disorder or ADHD is one of the most common developmental disorders that occur in children and adolescents. ADHD is a neurodevelopmental disorder characterized by disruptive levels of inattention, disorganization, hyperactivity and impulsivity. It occurs in childhood and causes difficulties that can be transferred into adulthood. It is a heterogeneous disorder that is difficult to diagnose and difficult to control. Prevalence data varies, but globally the prevalence is around 5%, while in the Republic of Croatia the prevalence of ADHD is 3% to 5% among school-age children. It occurs more often in boys than in girls; ADHD is four times more common in boys. The cause of ADHD is still not completely clear, and there are different theories about the causes of this disorder. ADHD occurs in three forms, namely the dominantly inattentive type of ADHD, the dominantly hyperactive-impulsive type of ADHD, and the combined type of ADHD. The diagnosis is made according to the guidelines of the American Psychiatric Association. According to the guidelines, ADHD is diagnosed in children with at least six symptoms from the group of inattention and/or hyperactivity/impulsivity, the symptoms must last for at least six months and occur to an extent that is not appropriate for the child's developmental stage and have a negative impact on social, academic or professional activities. The diagnosis is made in persons older than 17 years if five symptoms appear according to the already mentioned rule. ADHD has numerous unpleasant consequences for children and adults; for example, children with ADHD symptoms have behavioral and attention disorders that show up in different environments, they have difficulties in the family, their behavior is often not aligned with socially acceptable norms of behavior, and when they start school, they will have problems because their ability to learn it can be severely impaired by hyperactivity, impulsivity and difficulty maintaining attention. Educators of preschool children have an important role in recognizing the symptoms of ADHD in children and contribute to the timely diagnosis of this disorder, and with their interventions they can help the child, as well as his parents.