The Diagnostic and Statistical Manual, 4th Edition (DSM-IV) describes three types of ADHD:

• Predominantly Hyperactive-Impulsive Type
• Predominantly Inattentive Type and
• Combined Type.

Children with mainly the Inattentive type of ADHD tend to daydream and have difficulty focusing. The following criteria are used to diagnose children with ADHD, Predominantly Inattentive Type. Symptoms must have been present for at least six months, with onset before age seven:

• often fails to give close attention to details or makes careless mistakes in schoolwork, work, or other activities
• often has difficulty sustaining attention in tasks or play activities
• often does not seem to listen when spoken to directly
• often does not follow through on instructions and fails to finish schoolwork, chores, or duties in the workplace (not due to oppositional behaviour or failure to understand instructions)
• often has difficulty organizing tasks and activities
• often avoids, dislikes, or is reluctant to engage in tasks that require sustained mental effort (such as schoolwork or homework)
• often loses things necessary for tasks or activities (e.g. toys, school assignments, pencils, books or tools)
• is often easily distracted by extraneous stimuli
• is often forgetful in daily activities