Twenty children and young adults (age range 5 to 33 years, 12 females and eight males) with genetically confirmed 22q11 deletion syndrome (CATCH 22: Cardiac anomaly, Anomalous face, Thymus hypoplasia/aplasia, Cleft palate, and Hypocalcaemia), recruited from a large ongoing study, were given comprehensive assessments with a view to determining the pattern of neuropsychiatric and neuropsychological deficits thought to be part of the syndrome in many cases. IQ ranged between 46 and 100 with a mean score of 70. Half the group had an IQ <70. In 13 individuals, attention-deficit–hyperactivity disorder (ADHD), mainly inattentive or combined type in most cases, and/or autism spectrum problems were diagnosed. Many participants, even among those who had an IQ within the normal range and had neither ADHD nor autistic spectrum problems, showed a characteristic and pronounced behavioural profile with low mental energy, initiation difficulties, deficits in sustained attention, and social interaction (often augmented by limited facial expression and communication and speech problems).