The Register was aimed at assessing the benefit-risk profile of the treatment of attention deficit hyperactivity disorder (ADHD) with atomoxetine and methylphenidate. Post-marketing observational study, phase IV. Prescription medication to children and adolescents with ADHD aged between 6 and 18 years in the centres of reference for ADHD accredited by the Italian regions. In the period from September 2007 to October 2011, 1098 children and adolescents were treated with methylphenidate and 951 with atomoxetine. 411 (21.5%) patients are released from the register: 274 treated with atomoxetine and 167 with methylphenidate, with a greater risk of discontinuation for atomoxetine: RR 1.4 (1.3-1.6) p<0.001. The length of treatment at the time of removal from the register is 4.1 months for atomoxetine and 2 months for methylphenidate. Patients treated with atomoxetine are more likely to experience an adverse event compared to those treated with methylphenidate (RR 2.8; 1.9-4.2). The total number of serious adverse events observed was 110: 82 (75%) patients treated with atomoxetine and 28 (25%) individuals treated with methylphenidate. For 98 patients with serious adverse events, the adverse event led to the interruption of treatment with exit from the registry. The chance of a serious adverse event among those treated with atomoxetine compared to those with methylphenidate is RR 2.8 (1.8-4.2). There have been 14 cardiovascular events, all grown positively. 69 were found with a ECG alterations, with an increased risk for methylphenidate (RR 2.4; 1.4-4.2). The incidence of suicidal ideation was 4.5/1000 patients treated with atomoxetine. Hepatic alterations occurred with an incidence of 1/1000 subjects treated with methylphenidate and 4/1000 of those who received atomoxetine. The survey was carried out on a population which represents appropriately the paediatric population. The observed prevalence of ADHD corresponds to the expectation based on data from previous epidemiological investigations in Italy but considerably lower than what is reported in the international scientific literature. The rate of exposure to pharmacological treatments is similar to that of other European countries.