In children and adolescents with conduct disorder (CD), pharmacotherapy is considered when non-pharmacological interventions do not improve symptoms and functional impairment. Risperidone, a second-generation antipsychotic is increasingly prescribed off-label in this indication, but its efficacy and tolerability is poorly studied in CD, especially in young people with normal intelligence. The Paediatric European Risperidone Studies (PERS) include a series of trials to assess short-term efficacy, tolerability and maintenance effects of risperidone in children and adolescents with CD and normal intelligence as well as long-term tolerability in a 2-year pharmacovigilance. In addition to its core studies, secondary PERS analyses will examine moderators of drug effects. As PERS is a large-scale academic project involving a collaborative network of expert centres from different countries, it is expected that results will lead to strengthen the evidence base for the use of risperidone in CD and improve standards of care. Challenging issues faced by the PERS consortium are described to facilitate future developments in paediatric neuropsychopharmacology.