The legislation governing Ontario’s Greater Golden Horseshoe Greenbelt is set to be reviewed in 2015. This will be the first opportunity to review the defined boundaries of the protected area. This paper examines four other greenbelt areas to provide insight into how the province should deal with boundaries at the review. The case study areas are Ottawa’s National Capital Greenbelt, British Columbia’s Agricultural Land Reserve, London’s Metropolitan Greenbelt and Portland’s Urban Growth Boundary. Based on lessons from these case studies, the paper concludes with recommendations to provide a structure to the greenbelt review process, including harmonizing boundary definitions and exploring a more flexible approach to boundary definition.