ADHD is a common developmental disorder with onset in childhood that persists into adulthood in two-thirds of cases. The disorder is defined by symptoms of inattention, overactivity and impulsivity; however case-control, family and twin studies all find high rates of emotional lability that strongly co-vary with the core ADHD syndrome. 80% or more of adults with ADHD report significant levels of emotional lability, often severe, and causing impairments beyond that accounted for by inattention, hyperactivity or impulsivity. Drug treatments for ADHD have all been shown to improve symptoms of emotional lability. in children, a robust effect of methylphenidate has been demonstrated on aggression, although this has not been linked directly to the control of emotional symptoms. in contrast, the adult literature has focused more on emotional dysregulation, including affective lability, temper control and emotional over-reactivity. All these symptoms have been shown to improve following treatment with methylphenidate or atomoxetine, and to the same extent as core ADHD symptoms. Characterising the nature of the emotional symptoms in ADHD more detail, we found an increase in negative emotions such as frustration, anger and irritability, as well as an increase in their moment-to-moment variability. We conclude that patients with chronic forms of emotional instability should always be screened for ADHD, due to proven effectiveness of available treatments in the subgroup of emotionally labile patients who meet clinical criteria for ADHD.