Safety data concerning drugs usage in children are often inadequate, because most of marketed medicines have not undergone clinical trials involving children: therefore many drugs used in children are used “off-label” or “off-licence” in paediatric population. Furthermore, Adverse Drug Reactions (ADRs) are a significant problem in paediatric patients, and can be different from those observed in adults, because of the different weight and the incomplete maturity of organs and systems. Clinical trials involving children have been started only few years ago, and their results will be available in a long time; clinical trials will identify the more common and predictable side effects of medicines, but the rarest ones will be seen only when the drug will be used in larger numbers of patients, under the conditions of every day use. For these reasons, paediatric pharmacovigilance is essential, providing data on ADRs and drugs safety from both spontaneous reports and active surveillance program, e.g. post-marketing safety studies, and ad hoc epidemiological studies.