Although overall drug use remains low among women, with men three times more likely than women to use cannabis, cocaine or amphetamines, women are more likely than men to misuse prescription drugs, particularly prescription opioids and tranquillizers (UNODC, 2015). In addition, as described later in the document, there are indications that this ‘gender gap’ might be closing among girls. Yet, as it will become clear, only a very limited number of substance use prevention strategies target girls specifically and it cannot be assumed that existing evidence-based substance use prevention strategies benefit girls as much as they do boys. Moreover, it is estimated that, while one out of three drug users is a woman, only one out of five drug users in treatment is a woman. (UNODC, 2015). The overarching aim of this document is to inform and encourage governments, policy–makers, and other partners to take the necessary actions to implement evidence-based prevention strategies and treatment services for substance use disorders in order to provide everybody, girls as well as boys, and women as well as men, with the skills and opportunities to prevent the initiation of unhealthy behaviours and, in case of individuals who use drugs and suffer from drug use disorders, with the optimal support for improving their life circumstances.