The rule-based, normative, decentralized methods which enabled cities and regions to grow during the post-war era of industrialization and rural-urban migration now stand in the way of an easy adjustment of territories to the new economy, and make the pursuit of sustainable development objectives more costly and time consuming. How can these spatial planning systems change? Based on an exchange of countries’ experiences and analyses of the challenges of the 21st century, policy-makers and experts, meeting in Paris in 1999 and 2000 under a supervision of OECD, noted a growing convergence of planning practice in both federal and centralized countries with the respect to the role of the private sector, the priorities for government, and the importance of a broad, multisectoral approach. This overview of conclusions from the Paris meetings defines the cutting edge of a field that will be critical to successful economies in the future.