In Sweden, local and regional planning practices are faced with the challenge of managing rapid growth in expansive urban regions. However, spatial planning should also contribute to the fulfilment of formalized sustainability objectives and support sustainable development. This includes addressing cross-cutting sustainability issues that transcend established administrative and territorial boundaries. Thus, the management of sustainability issues requires attention from actors at different levels, and challenges how contemporary planning practices plan for development. Based in the expansive Stockholm region, this study explores the cross-level interaction in spatial planning and decision-making and planning practitioners’ experiences and apprehensions of contemporary municipal planning practices with a focus on statutory plans to achieve sustainability targets and objectives. The results show that municipal planning organizations are under pressure because of rapid urban expansion. It is concluded that the role, format and content of statutory as well as informal planning instruments are decisive for the cross-level interaction between planning levels. Moreover, planning instruments find new trajectories resulting in mismatches in expectations from planners at adjacent planning levels. This influences the interplay and preconditions for achieving national and regional sustainability targets and objectives.