Governance dynamics and spatial planning regulations are significant factors in the occurrence (or containment) of urban sprawl. However, qualitative investigations of the planning regulatory systems and practices, and governance arrangements that cumulatively stimulate suburbanisation, typically remain detached from land-change analyses. Based on the concept of institutional frames of spatial planning systems, this article elucidates how governance dynamics and spatial planning practices, at different scales, can partially explain suburban land-use patterns. The territorial transformations of two Southern European metropolitan regions, Barcelona and Milan, are examined through land-use data (1990–2012) at different territorial scales. Demographic (1991–2011) and administrative (2011) data are also analysed. In-depth interviews about individual and collective land management practices have been carried out, as well as document analysis concerning spatial planning laws and regulations. This research shows that the metropolitan character of urban sprawl originates from local planning practices mainly performed by municipal authorities through land-use micro-transformations. Further, it highlights the decisive role that higher-level institutions can play in land containment. Urban sprawl is hence not necessarily an unplanned phenomenon, but rather a ‘differently planned’ local and regional land-use strategy. 治理机制和空间规划法规是城市蔓延发生（或受到遏制）的重要因素。然而，规划监管体系和实践的定性调查以及累积式刺激郊区化的治理安排通常与土地变迁的分析脱节。基于空间规划系统框架的概念，本文阐述了不同规模的治理机制和空间规划实践如何部分解释了郊区土地利用模式。我们通过土地利用数据 (1990–2012) 在不同的地域尺度上考察了南欧两个大都市区巴塞罗那和米兰的领土转变。文章同时分析了人口数据 (1991–2011) 和行政 (2011) 数据。我们对个人和集体土地管理实践做了深入采访，并记录了对空间规划法律法规的分析。本研究表明，大都市的城市蔓延源于当地主要由市政当局通过土地利用微调而实施的规划实践。此外，它凸显了上级机构在土地遏制方面可以发挥的决定性作用。因此，城市蔓延不一定是一个无计划的现象，而是一个“以不同方式规划”的地方和区域土地利用战略。