The 22q11 microdeletion syndrome (22q11-DS) is strongly associated with schizophreniform disorders and, in turn, the 22q11 deletion region harbours several candidate genes for schizophrenia. Here, we present the case of an adolescent female patient with 22q11-DS associated with impaired cognitive abilities and behavioural abnormalities. The patient was studied with magnetic resonance imaging (MRI) and positron emission tomography (PET) as well as extensive neurophysiological investigations. Although no structural or functional abnormalities were found in MRI and PET, assessment of event-related potentials elicited during the Continuous Performance Test revealed a lack of NoGo anteriorisation. The latter was replicated in a second case of 22q11-DS with schizoaffective disorder but devoid of a severe somatic syndrome. This electrophysiological finding, which indicates modified functioning of the cingulate gyrus, has previously been demonstrated only in patients suffering from schizophrenia and attention deficit/hyperactivity disorder, two psychopathological conditions frequently associated with 22q11-DS. We conclude that more extensive study of NoGo anteriorisation as a potential endophenotype of 22q11-DS patients at risk for 22q11-associated psychiatric conditions is warranted.