Questions that are tagged with ADHD should be about coping strategies for parenting and educating these children and the special situations that occur because of their diagnosis.
Many children diagnosed with ADHD have a very difficult time sitting still or participating in the average classroom setting without incurring behavioral consequences for movements over which they have little control. They also may have a difficult time focusing well enough to complete common tasks given at school. For these reasons, children with ADHD are often medicated to help decrease incidence of overactivity and increase focus and attention span. About 3-5% of today's children have been diagnosed with this disorder making it the most common behavioral disorder affecting children today.
In the most severe cases ADHD is often coupled with other disorders such as Tourette's or Bi-polar disorders. ADHD sypmptoms can overlap with these disorders as well as depression, anxiety and others so diagnosis must be made carefully.
For a more detailed list of symptoms, synopses of types of treatments, and listing of tests that are administered to determine a diagnosis of ADHD or not, check out these more in-depth links.