The overall objective of this study is to assess the optimal use of ‘blended instruments’, a combination of grants and market-based Financial Instruments (Fis) in possible post 2020 EU investment support instruments. Blended instruments have the advantageous to support project with high socio-economic benefits, the costs of which can be higher than the potential revenue of the project. In the context of more effective use of EU budget resources, this study on the future possibilities to address market failures is important. Twofold purposes are identified to answer to this study, on one hand, to review the best practices and performance of existing EU blending instruments to list the characteristics of instruments available and the market failure they intend to address; on the other hand, to identify principles for determining the optimal mix for each target group in view of the next Multi-Financial Framework. The scope of the study is wide because it covers 2014-2020 EU financing policy and all Directorate General’s (DG) intervention. The team of the study bases its analysis on literature review, interviews with policy experts and researchers to understand the theory behind the instruments. In a next step, 10 case studies are selected to describe the use of the existing instruments. The last step of the methodology is to organise a workshop with the EC and external stakeholders to discuss on modelling of post 2020 EU financial policy.