Attention deficit/hyperactivity disorder (ADHD) is a common psychiatric disorder characterized by symptoms of inattention, hyperactivity and impulsivity. There is an ongoing discussion whether symptoms of emotional dysregulation should be added to the conceptualization of ADHD in order to describe the psychopathology of ADHD more precisely, at least in adult patients. Symptoms of emotional dysregulation are well defined and seem to be distinct factors of the psychopathology of adult ADHD. Assessment of this psychopathological dimension has shown sufficient reliability and validity. Empirical studies have confirmed a high prevalence of this psychopathological feature in adults with ADHD that compares to the frequency of the ADHD core symptoms, inattention, hyperactivity and impulsivity. Evidence is given that emotional dysregulation has an independent effect on social problems associated with ADHD in adult life. Moreover, pharmacological and psychotherapeutic interventions help to ameliorate emotional dysregulation together with symptoms of inattention and hyperactivity/impulsivity. Thus, there is growing evidence that emotional dysregulation might be recognized as a core feature of ADHD.