Many methods are available to support adaptation planning. Yet there is little guidance on their selection. A recently developed diagnostic framework offers a structured set of criteria to choose research methods for specific adaptation questions. It has been derived from science-driven cases mostly. This paper offers the first application to a policy-driven case. Thus, it aims to (1) assess the descriptive quality of the framework for adaptation planning and (2) reflect on its value in supporting method selection. The paper focuses on the research commissioned for adaptation policymaking by the Dutch Delta Programme in the Wadden region. It compares the research methods used in the Delta Programme with those suggested by the diagnostic framework. It concludes that the selection of methods in the adaptation planning process can be described quite well by the decision trees of the diagnostic framework. Deviations occurred mostly for pragmatic reasons when the selection is informed by practical limitations of the policymaking process, such as available resources, time constraints and experience of the involved experts. It is recommended to enrich the diagnostic framework with methods from adaptation practice and consult it in climate adaptation studies at an early stage.