Youth remain starkly underrepresented in parliaments across the globe. Under these conditions of descriptive underrepresentation, who are the parliamentarians bringing youth concerns to the legislative arena, and what motivates them to do so? This chapter examines the dynamics of youth’s substantive representation through a cross-national analysis of written parliamentary questions in the Netherlands, France, the UK, and Germany, using a multilingual youth dictionary. Adopting an issue salience approach, understanding substantive representation as the attention dedicated to youth in parliamentary questions, this chapter proposes a theoretical framework distinguishing opportunity and incentive structure. Representational behaviour may be driven by increased awareness of youth issues (opportunity) or from strategic motivations to gain political capital (incentive). Using multilevel negative binomial regression models, the analysis finds that younger, economically left-leaning MPs and those from parties with large youth constituencies submit more youth-related questions. These results underline the importance of both descriptive presence and electoral engagement for ensuring the substantive representation of youth in democratic institutions.