Developing a criminal justice model that includes a comprehensive assessment of juveniles in conflict with the law is crucial to making appropriate, swift and efficient decisions at the different levels of the criminal proceedings. Several legal instruments have focused on ensuring rights in juvenile criminal proceedings, but Directive 2016/800 is the most recent and important document at the European level. The Directive is an unprecedented, legally binding instrument focusing exclusively on suspected and accused minors. It addresses various legal issues and objectives related to the specific needs of minors by providing for an individualised assessment. On the one hand, an individual assessment can be considered a prerequisite for evidence-based decision-making. On the other hand, it provides an opportunity to listen to, advocate for and engage with the young person, take into account their particular circumstances and create a favourable environment for subsequent behavioural improvement. By setting out general principles, Directive 2016/800 gives Member States considerable flexibility in the implementation and application of individual assessment of children within their respective national systems. The aim of this chapter is to analyse the challenges and current practices of individual assessment in two EU Member States, Croatia and Lithuania. Best practices from these two countries are presented in this chapter to illustrate the need for a child-first, multidimensional, interdisciplinary and multi-professional approach in the investigation of children in conflict with the law.