There is a well-known knowledge gap regarding the efficacy and safety of medicines in children of all ages and children are often treated with medicines off-label. Children are thus deprived of treatment based on the same quality of information that guides treatment in adults. The knowledge gap regarding efficacy and safety of medicines in children has been acknowledged by authorities and is reflected in legislation both in North America and in the European Union. Recent reports on the effects of legislation indicates that paediatric clinical trials remain a challenge. Paediatric clinical trials are needed in the entire developmental age spectrum and are especially needed in certain therapy areas. Paediatric clinical trials have special features compared with trials in adults, and these need to be taken into account. These special features include scientific issues related to small samples and heterogeneity, the consent/assent procedure, the need for age-appropriate study information, specific outcomes and safety issues related to development and maturation. Competence in paediatric clinical trials is required in both designing, planning, co-ordinating and organising paediatric clinical trials, as well as research infrastructure and networks to increase power and disseminate information and expert advice. Strengthening of paediatric clinical research is essential to facilitate generating the data that will let children enjoy new medical advances in a similar manner as adults.