Because of a lack in drug evaluation in children, they receive many off license drugs prescription, which means drugs prescribed in an indication, dosage, formulation or age different from the license terms. However, drug evaluation is crucial in paediatrics population because of pharmacokinetics and pharmacodynamics modifications throughout organism development, which make usually wrong any extrapolation to children of data obtained in adults. Drug safety is generally better in infants except in newborns who are at a particularly high drug-related risk because of high frequency of off license drug use, many drugs association and drugs metabolism immaturity. The lack of evaluation in children, the fact that children are the unique target population of some drugs or the maturation phenomena explain some adverse effects more specific in children. The more the children are young, the more they are exposed to medication or drug utilization errors. Physician must take what the SPC, as found in the Vidal dictionary, mentions about children into account while prescribing. Drugs with a paediatric license must be preferred overall, however it should be kept in mind that a paediatric license means only that the drug is active in the indication of the license but it doesn't position it regarding other therapeutic alternatives. Off labeling prescription should be based on a supposed benefit, which had to be justified if a severe side effect occurred.