This study summarizes the most important aspects of integrating modelling into Maritime Spatial Planning (MSP) and Strategic Environmental Assessments (SEA). The results are part of an evaluation carried out in the framework of the EU BaltSeaPlan (BSP) project. The findings are based on a multi-disciplinary assessment carried out by a working group composed of spatial planners, managers and environmental scientists under participation of the BSP community through a number of workshops and group discussions. The overall goal of the study was to identify the most important planning questions and the modelling requirements to adequately address these questions. In addition, the study provides illustrative case studies, e.g. an ecosystem evaluation framework, habitat modelling, and offshore wind site selection modelling.