The aim of this report is to assess the effectiveness of measures for the prevention of substance abuse drawing on high quality surveys including reviews and meta-analyses. Effectiveness, in this context, means impact in preventing, delaying or reducing children's and young people's consumption of tobacco and alcohol as well as cannabis and other illicit psychoactive substances. The study covers preventive measures that are both behavioral and environmental (i.e. based on consumption environment and context). It presents conclusions about the effectiveness of measures in a range of settings as well as substance-specific conclusions. The conclusions reported are rated according to the strength of the evidence on which they are based. Observations on gender-specific effectiveness, on negative consequences of addiction-prevention measures and on efficiency are also included. In addition, the theoretical background to effective measures is described and assessed.--Publisher's description.