This study is an enquiry into the legal developments aimed at bringing the involvement of children in armed conflict to an end. The issue of children's recruitment into and use by armed groups and forces is addressed from an interdisciplinary legal perspective that combines human rights law, international humanitarian law and international criminal law. The study takes a child rights-based approach to the issue of children in armed conflict and thereby aims to fill some of the current gaps in the international criminal law-discourse, which has not been developed with special regard to children's rights. Part I of the study analyses the evolution of the qualification of the acts of recruiting and using children in armed conflict, from violations of the laws of war to human rights violations and, more recently, international crimes. It describes the growing legal framework surrounding this phenomenon, and places emphasis on a few issues of particular relevance, such as the term 'child soldier' or 'voluntary' versus 'forced' recruitment. It is argued that in order to tackle the problem of children involved in armed conflict, the child must be appropriately defined and taken into account by international law and justice mechanisms. Part II of the study seeks to assess the consequences of the international standard-setting regarding children in armed conflict on international and domestic legal practice. The evolving international case law relative to the crimes of recruiting and using children in armed conflict is analysed, followed by an examination of the tendency to criminalise these acts at national level. In order to illustrate this point, the last chapter of the study focuses on the relevant legal developments of two countries particularly affected by the use of children in armed conflict, namely Colombia and the Democratic Republic of Congo. In conclusion, an attempt is made to answer the question as to whether the judicial path is efficient or desirable when addressing the issue of children's involvement in armed conflict.