Currently little is known about how institutional arrangements co-evolve with urban experimentation. This paper mobilizes neo-institutional literature and recent urban experimentation literature as a framework to explore how and why institutional arrangements differ across urban contexts. Empirically the paper focusses on smart city initiatives in Amsterdam, Hamburg and Ningbo. These three cities are frontrunners in adopting a comprehensive smart city agenda, but they do so in different ways. The paper examines regulative, normative and cognitive elements of institutional arrangements, explores how they shape experimentation, and reflects on their place-based specificities. The comparative analysis suggests that the focus of, and approach to, experimentation can be understood as resting in a (possibly unique) combination of strategic agency and dynamics at multiple spatial scales.