In times of pervasive party membership decline and ageing of political parties, young people that join one of the professionalised former catch-all parties are a rare species. But this group is exceptionally important as future political decision makers are most probably among them. This work analyses the motivations, experiences and future perspectives of young members in the German Social Democratic Party (SPD). Based on rich data, both qualitative and quantitative, it models the differences between different types of party members, based on their motivation and their future perspectives between career building and exit. The work uses two very different strands of literature, on individual participation and on party organisation change. On the individual level, it is based upon classic resources-based and incentive-based theories of political participation and on the organisation level, it draws upon the notions of the cartel party and electoral-professional party. The study is guided by three research questions that put the emphasis on the individual level: What made young party members join a party? How do these members experience the party? How do young party members envision their future in the party? The results show differences and potential areas of conflict between members; between potential future decision makers and potential future grass-root members as well as between young and old and students and non-students. It supports the assumption that these professionalised parties cannot count on their old milieus to provide them with a stable membership. The young members decide about their future in the party depending on what influence the party offers them. But this perception differs between potential leaders and potential leavers. The gap between perceiving intra-party influence as sufficient or as insufficient potentially leads to a future further divide between party leadership and other members and should be an area of concern for party organisations.