ENHistorically, children as victims in criminal procedure had a specific status in European countries. Several Council of Europe and European Union documents invite countries to grant particular rights to children in criminal procedure. The current main document the countries need to adhere to is Directive 2012/29/EU, establishing minimum standards on the rights, support, and protection of victims of crime. Although the European countries follow the same direction, the development, rationale, and steps taken in the Member States differ due to various factors. For example, in Lithuanian criminal procedure, there is no separate notion of “vulnerable persons”. However, children have always received a higher standard of protection, which at some point is different from the current European standards, to which the country is gradually striving to comply. A similar normative approach can be found in Croatian criminal procedure, which grants children special protection without specifying their vulnerability. However, Art. 43a Para 2 of the Code of Criminal Procedure obliges the criminal prosecution authorities to pay special attention, inter alia, to victims who are particularly vulnerable due to their relationship with the perpetrator. While the concept of vulnerability is subtly revealed in the most important procedural normative act, the special vulnerability of children due to their age is explicitly acknowledged in the Criminal Code. The chapter describes the concept of vulnerability and vulnerability of children, assesses the criteria to define the vulnerability of children in EU laws governing criminal procedure, as well as provides a case analysis of the national legal systems of Croatia and Lithuanian with an aim to understand the context which explains national peculiarities and the particular provisions governing the establishment and assessment of child victims’ vulnerability.