A large amount of the current literature has focused on the characteristic symptoms of attention deficit hyperactivity disorder (ADHD) in children and adolescents. In contrast, less attention has been devoted to ADHD clinical subtypes in adult patients. We evaluated 164 consecutive adult ADHD (A-ADHD) outpatients using DSM-5 criteria and many specific rating scales and questionnaires. A principal component factor analysis was performed on clinical and symptomatological variables to describe potential clinical variants. We sought to determine different A-ADHD variants focusing on demographic and clinical features. A four-factor solution was identified, and patients were clustered, according to their z-score, in 4 subgroups. The first was marked out by Emotional Dysregulation (ED), the second by Substance Use (SU), the third by Core-ADHD Symptoms (Co-ADHD) and the fourth by Positive Emotionality (PE). Predominantly ED patients showed worse overall function, early treatment with antidepressants and a greater presence of borderline personality disorder than predominantly Co-ADHD patients. Predominantly SU patients reported high rates of bipolar disorder and severe general psychopathology. The PE factor was related to hyperthymic temperament and hypomania and showed a higher level of functioning. Females with A-ADHD showed a lower risk of being included in SU, and A-ADHD patients with co-occurring delayed sleep phase had less risk of being included in the SU factor than the prevailing Co-ADHD group. Our empirically based description of four clinical A-ADHD variants shows several aspects beyond the definition given by the DSM-5 diagnostic criteria.