Sub-national governments (SNGs) are key players for public investment in OECD countries, responsible for nearly two-thirds of it. At the same time, both the well-being of the population and economic performance depend on an adequate provision of public services, which require public facilities and thus public investment. Ensuring that sub-national governments command the resources for necessary public investment is hence important. While in the immediate, the fiscal space of a SNG for public investment is basically determined by its current fiscal capacities, in a longer-term perspective the evolution of fiscal space comes to depend increasingly on the institutional context. This includes the national framework of fiscal relations across levels of government, the nature and characteristics of SNGs’ revenue sources and spending responsibilities, SNGs resilience to crises, and their structural ability to borrow. This paper explores the institutional ability of SNGs to influence their fiscal space for public investment. In this context, it also analyses the main challenges to be faced by SNG finances in the decades to come, as well as recent reforms implemented by SNGs to tackle these specific issues.