Relatively little research has been conducted on quantitative electroencephalography (QEEG) activity in patients with psychosis÷schizophrenia, especially in populations at-risk for the illness. Further studies are needed, in order to offer a possible endophenotypic marker of the cerebral functioning, associated with psychosis÷schizophrenia, in correlation with the neuroimaging, the neurocognitive, biochemical, molecular genetic tests, clinical aspects and the EEG activity from the same subjects. The aim was to investigate the role the QEEG abnormalities play in the etiology of psychosis÷schizophrenia, whether it can provide an endophenotype for psychosis and to make some correlations with the results obtained through magnetic resonance (MR) spectroscopy, for proper early detection and intervention. The prospective research was performed in the University Clinic of Child and Adolescent Psychiatry, Timisoara, Romania, involving 55 children with schizophrenia or ultra high-risk (UHR) for psychosis (groups 1, 2, 3 and 4) and 55 children as healthy controls (group 5). Groups 1 and 2 (28 children) are diagnosed with schizophrenia, groups 3 and 4 are UHR for psychosis (27 children), and group 5 represents healthy controls. Groups 1 and 3 had convulsive seizures in their personal history. We noticed: through the QEEG, numerous patterns of theta and delta activity, the diminished amplitude of the alpha band waves and the diminished alpha activity; also, the onset of psychosis was earlier at those presenting convulsive seizures in their personal history (groups 1 and 3); also, specific neuroimagistic abnormalities and modifications. The cerebral lesions, appearing during the development, raise the liability for schizophrenia. The high-risk for schizophrenia is correlated with the personal history of epilepsy, as well as with the family risk for psychosis.