Attention deficit hyperactivity disorder (ADHD) is one of the most common neurodevelopmental disorders in children, affecting approximately 5% children in Europe. Methylphenidate (MPH) is the most-commonly prescribed medication for ADHD children; it is also increasingly used in ADHD adults. In 2007, the European Commission requested a referral to the Committee for Medicinal Products for Human Use (CHMP) under Article 31 of Directive 2001/83/EC, as amended, for MPH because of safety concerns. The CHMP concluded that study of the long-term effects of MPH on growth, sexual development, neurological system, psychiatric states and cardiovascular system is needed. In response to the CHMP’s concerns, the ADDUCE (Attention Deficit Hyperactivity Disorder Drugs Use Chronic Effects) research team has been formed by a consortium of experts in the fields of ADHD, drug safety, neuropsychopharmacology and cardiovascular research. The ADDUCE project aims to investigate the long-term adverse effects of MPH on growth, neurological system, psychiatric states and cardiovascular system in children and adults. The ADDUCE team will use multiple pharmacoepidemiological research methods to achieve its aim: (1) Retrospective analysis of existing databases. (2) 2-year prospective cohort study recruiting 800 MPH-treated children and adolescents and 800 controls. (3) Cross-sectional study (600 MPH-treated patients and 600 controls) in late adolescents and young adults. Furthermore the ADDUCE team will develop research tools for the evaluation of adverse effects of MPH on cognition and motivation. The ADDUCE consortium comprises 12 academic partners, 1 SME and 1 EU professional network. The ADDUCE team will directly interact with the European Medicines Agency to assist them in making regulatory decisions on the safety of MPH in children and adults. The ADDUCE team will adopt an open-access policy to ensure the information and results have the maximum public health impact.