This chapter focuses on normative electroencephalography (EEG), or qEEG data that are compared to a control group or normative database. It also limits the application of qEEG to neuropsychiatric conditions and focuses on more strictly neurological applications that fall beyond the scope. Abnormal EEG findings consist of the so-called "paroxysmal" or "epileptiform discharges." The estimated incidences of paroxysmal EEG in some attention deficit hyperactivity disorder (ADHD) groups were around 12-13% to approximately 30%, which are high as compared to 1-2% in normal populations. The exact implications of such EEG activity in subjects without overt signs of epilepsy are not very well understood and many neurologists will see no need to treat these subjects as epileptics. With the introduction of qEEG and computerized EEG analysis many more studies are carried out investigating the neurophysiology of ADHD.