The primary features of ADHD include inattention and hyperactive-impulsive behavior. ADHD symptoms start before age 12, and in some children, they're noticeable as early as 3 years of age. ADHD symptoms can be mild, moderate or severe, and they may continue into adulthood. ADHD ADHD ADHD ADHD occurs more often in males than in females, and behaviors can be different in boys and girls. For example, boys may be more hyperactive and girls may tend to be quietly inattentive. ADHD There are three subtypes of ADHD: ADHD 
Predominantly inattentive. The majority of symptoms fall under inattention.
Predominantly hyperactive/impulsive. The majority of symptoms are hyperactive and impulsive.
Combined. This is a mix of inattentive symptoms and hyperactive/impulsive symptoms.
 Inattention A child who shows a pattern of inattention may often: 
Fail to pay close attention to details or make careless mistakes in schoolwork
Have trouble staying focused in tasks or play
Appear not to listen, even when spoken to directly
Have difficulty following through on instructions and fail to finish schoolwork or chores
Have trouble organizing tasks and activities
Avoid or dislike tasks that require focused mental effort, such as homework
Lose items needed for tasks or activities, for example, toys, school assignments, pencils
Be easily distracted
Forget to do some daily activities, such as forgetting to do chores
 Hyperactivity and impulsivity A child who shows a pattern of hyperactive and impulsive symptoms may often: 
Fidget with or tap his or her hands or feet, or squirm in the seat
Have difficulty staying seated in the classroom or in other situations
Be on the go, in constant motion
Run around or climb in situations when it's not appropriate
Have trouble playing or doing an activity quietly
Talk too much
Blurt out answers, interrupting the questioner
Have difficulty waiting for his or her turn
Interrupt or intrude on others' conversations, games or activities
 Typical developmental behavior vs. ADHD Most healthy children are inattentive, hyperactive or impulsive at one time or another. It's typical for preschoolers to have short attention spans and be unable to stick with one activity for long. Even in older children and teenagers, attention span often depends on the level of interest. The same is true of hyperactivity. Young children are naturally energetic — they often are still full of energy long after they've worn their parents out. In addition, some children just naturally have a higher activity level than others do. Children should never be classified as having ADHD just because they're different from their friends or siblings. ADHD Children who have problems in school but get along well at home or with friends are likely struggling with something other than ADHD. The same is true of children who are hyperactive or inattentive at home, but whose schoolwork and friendships remain unaffected.