Disorders in behaviour are an area of interest whose study has developed intensively during the 20th and 21st centuries. Disorders are more often recognized in time, and can therefore be helped in an adequate way. It is crucial to recognize the disorders in time and treat them in a quality way as this ensures the child's proper and stable development. Also, it’s important that adults in the child's environment, especially parents, have the ability to recognize and distinguish various disorders. Parents must also be aware of how the child and they can be helped, and how they are not alone in a challenging situation. All preschoolers are mischievous, defiant and impulsive sometimes, but that is common for children at that age. However, there are children who express different kinds of behaviors that are not normal for their age. They can occur due to certain stressors in a child’s life that are temporary or they can be a result of more permanent disorders. The most frequent disorders in a child’s behaviour involve various forms of behavioral disorders as well as attention deficit hyperactivity disorder. Boys suffer from behavioral disorders more often than girls. Children sometimes behave undesirably even around adults. If different disorderly behaviours are not common for the child’s age or if they carry on for an extended period of time, it can be said that there is a certain disorder in behaviour. It is impossible to say why a certain disorder appears, but there is a great variety of factors that can play part in the appearance.