ADHD in children is a well-defined disorder that has been carefully researched and documented in the literature for many decades and is listed as a specific disorder in the DSM-IV-TR (American Psychiatric Association, 2000). On the other hand, ADHD in adults has only recently been described and separated from childhood ADHD by its differing symptom list and associated dysfunctions. Adult ADHD is described as a specific disorder in DSM-V (APA, 2013).
The best recent source for the characterization of adult ADHD is, ADHD in Adults: What the Science Says, by Russell Barkley, Kevin Murphy, and Mariellen Fischer, The Guilford Press 2008. This important book is a result of a carefully conducted research study using excellent control populations to characterize ADHD in adults, their symptoms, their evaluation by various psychological tests, and treatment options. The study shows the profound implications of having ADHD relative to the educational and occupational functioning of the adult, as well as with drug use and driving/antisocial behavior. Of particular interest is that the study concluded that easy distractibility is a seminal feature of the disorder. The book lists nine best symptoms for the diagnosis of ADHD in adults. The book also concluded that neuropsychological tests were not necessarily recommended nor particularly informative in the diagnosis of ADHD in adults, but could instead be used to assess specific cognitive impairments.
Treatment options include evidence that specific medications (such as some stimulants and atomoxetine) are sometimes effective in reversing some of the deficits in executive functioning that are present in adults with ADHD. Adderall (mixed amphetamine salts) has been supplanted by the newer drug Vyvanse (lisdexamfetamine) as the most popular psychostimulant for the treatment of ADHD. A comparison of these two drugs can be found here.
Quantitative EEG (also known as QEEG) has been used as part of the evaluation and treatment of ADHD. (www.q-metrx.com). This diagnostic test can demonstrate defects in the frontal lobes of the adult and child ADHD. QEEG also is sometimes useful in defining treatment modalities for use of brain wave neurofeedback. Some studies have concluded that neurofeedback is effective in the treatment of childhood ADHD. It is less clear if it is effective in treating adult ADHD.