Inattention and hyperactivity/impulsivity are the key behaviors of ADHD. Some people with ADHD only have problems with one of the behaviors, while others have both inattention and hyperactivity-impulsivity. Most children have the combined type of ADHD. In preschool, the most common ADHD symptom is hyperactivity. It is normal to have some inattention, unfocused motor activity, and impulsivity, but for people with ADHD, these behaviors:Are more severe Occur more often Interfere with or reduce the quality of how they function socially, at school, or in a job.