A number of children present to the physician or the professional with attentional symptoms that are caused by medical problems that is not related to ADD or ADHD; but, at the end of the day, it looks like that to the teachers or the parents.
The first condition is called adenoid hypertrophy, which causes snoring in certain children and sleep apnea. While this is a rare cause of problems in children, it should be identified and treated, so the create diagnosis is made.
In younger children, especially in boys who are hyperactive and less than five years of age with attentional difficulties and extreme hyperactivity, lead poisoning should always be ruled out.
Third, while it is very rare, some thyroid issues will present with attentional issues; so laboratory testing, especially if there is a family history, would be appropriate.
Last, but not least, in the history it's important to make sure that the child does not suffer from some other psychiatric condition, particularly, anxiety disorders. Many children are anxious, will look, for all intents and purposes, will look like they have ADHD. In other words, they are distractible and inattentive. There may be behavior problems under certain circumstances. That history is critical in making sure that we are not making a diagnosis of ADD, when the real diagnosis is anxiety disorder.