To make ADHD diagnoses more consistent, the APA has grouped the condition into three categories, or types. These types are predominantly inattentive, predominantly hyperactivity-impulsive, and a combination of both.

As the name suggests, people with this type of ADHD have extreme difficulty focusing, finishing tasks, and following instructions.

Experts also think that many children with the inattentive type of ADHD may not receive a proper diagnosis because they don’t tend to disrupt the classroom. This type is most common among girls with ADHD.

People with this type of ADHD show primarily hyperactive and impulsive behavior. This can include fidgeting, interrupting people while they’re talking, and not being able to wait their turn.

Although inattention is less of a concern with this type of ADHD, people with predominantly hyperactive-impulsive ADHD may still find it difficult to focus on tasks.

This is the most common type of ADHD. People with this combined type of ADHD display both inattentive and hyperactive symptoms. These include an inability to pay attention, a tendency toward impulsiveness, and above-normal levels of activity and energy.

The type of ADHD you or your child has will determine how it’s treated. The type you have can change over time, so your treatment may change, too. Learn more about the three types of ADHD.