Political parties are complex organizations. They must respond to a variety of institutional expectations and operate in a tension between professionalized political careers and volunteer-based member associations. The study offers a theoretically grounded, comparative analysis of the organizational structure and culture of German parties. It examines the relationship between the legal requirements for parties and the structural reality of organizations. Additionally, the study provides insight into the Party Central Offices: What organizational ideals shape professional party management, what significance do party members hold today? And what impact have the party reforms of recent years, which aimed to strengthen intra-party participation, had on professionalized member parties?.