People with Oppositional Defiant Disorder (ODD) display a pattern of negative, hostile and defiant behavior lasting for at least six months. The disturbance in behavior causes significant difficulty in social, academic, or occupational life.

The disorder usually becomes evident before age 8 and not later than early adolescence, with symptoms usually appearing in the home setting, but over time appearing in other settings as well. People with this disorder do not see themselves as defiant, but justify their behavior as a response to unreasonable demands or circumstances. Over months or years, the disorder may progress to Conduct Disorder.

ODD is believed to affect between 1 and 11% of the population, with an average prevalence of around 3.3%. The disorder is somewhat more common in males than females before puberty, but is about equal after puberty. The symptoms are similar in each gender, with the exception that males are may be more confrontational and have more persistent symptoms.