This paper assesses the embedding of land use and transport instruments—Planning Support Systems (PSS), models and tools—in Dutch planning practice, in order to shed light on how planning practitioners perceive these instruments and to ascertain the reasons and manner of their (lack of) utilization. These insights provide much-needed input to improve support instruments for integrated land use and transport planning, particularly during early planning phases and on the regional level. The research adds to the emerging literature on PSS. It builds on general insights into bottlenecks that block the use of PSS in practice, and employs a user-oriented approach to gain more insight into how users perceive these bottlenecks and how they relate to specific land use and transport PSS. Much of the existing research geared toward improving these instruments has a technical focus on adjusting the intrinsic workings of the instruments themselves. However, the way in which they are embedded in planning practice has remained largely ignored and poorly understood. Based on data from a web-based survey administered to land use and transport practitioners in the spring of 2007, this paper describes how LUT instruments are embedded in planning practice and how they are perceived by the planning actors in land use and transport planning. The findings suggest that a technical focus is insufficient to improve the implementation of these instruments. The key bottlenecks, identified by the survey, actually are centered on "softer issues," such as lack of transparency and poor connections to the planning process. The closing analysis and discussion offer some potential remedies for these shortcomings.