CAFEPS was a multicentre, case-control study investigating clinical, neuropsychological, neuroimaging, biochemical, immunological, and genetic variables in patients with early-onset first-episode psychosis in Spain. Participants were recruited between 2003 and 2005, and included 110 patients aged between 9 and 17 years diagnosed with a first episode of psychosis, and 98 matched healthy controls. Patients were recruited from child and adolescent psychiatry units at six university hospitals within five Spanish cities (Madrid, Barcelona, Vitoria, Santander, and Pamplona), and controls were recruited from the same geographical areas and matched for gender and age. After baseline, participants completed follow-ups at 6 months, 1 year, and 2 years with clinical, neuropsychological, neuroimaging, and biochemical assessments repeated at the two-year follow-up visit.