In order to address urban challenges Urban Living Labs (ULL’s) are set up as new forms of partnership between state, (market) and civil society. The primary governance challenge of ULL’s is to effectively use their liminal in-between position to create livable cities. However, liminal space at the same time is claimed to generate certain risks in terms of legitimate decision-making and accountability. By zooming in on the empirical case of ULL’s in a large Dutch city in the Randstad area the authors ask: Which key value trade-offs are made in the liminal space of ULL’s and which new institutional rules emerge in order to deal with these trade-offs? In this chapter the authors identify the following trade-offs: institutional collaboration versus autonomous activism, professional versus lay participation and values, the social versus the material, place bound experimentation versus placeless learning and accountability and capital value versus societal value. Calls for new institutional rules for city making to deal with these trade-offs can potentially address the lack of legitimacy in decision-making, yet may also hamper the open-ended nature of experimentation by introducing bureaucratic procedures and co-opting labs into implementing formal policy.