Its features included an enduring pattern of severe, developmentally-inappropriate symptoms of inattention, hyperactivity, and impulsivity across different settings (e.g., home and school) that significantly impair academic, social, and work performance.

[1] It was classified in the World Health Organization's ICD-10 and was roughly similar to the "combined presentation" of attention deficit hyperactivity disorder in the American Psychiatric Association's DSM-5.

Cognitive impairment and delayed language and motor development were more common in this group than in the general population, and they might have experienced low self-esteem and engaged in antisocial behavior as a consequence of the disorder.

[3] Though the American Psychiatric Association's criteria for Attention Deficit Hyperactivity Disorder (ADHD), and the World Health Organization's criteria for hyperkinetic disorder each list a very similar set of 18 symptoms, the differing rules governing diagnosis meant that hyperkinetic disorder featured greater impairment and more impulse-control difficulties than typical ADHD, and it most resembled a severe case of ADHD combined type.

[1] Once the patient and family had been educated about the nature, management and treatment of the disorder and a decision has been made to treat, the European ADHD Guidelines group[6][7] recommended medication rather than behavioral training as the first treatment approach; and the UK's National Institute for Health and Clinical Excellence recommended medication as first line treatment for those with hyperkinesis/severe ADHD, and the provision of group parent-training in all cases of ADHD.