This paper presents a new doctoral research project on legislative coordination in multi-level systems. The aim of the project is to assess how parties and parliaments coordinate across the different levels of government and governance in modern liberal democracies. The project takes the general position that coordination (and cooperation) between levels should be easier when the same parties are in power, and more difficult when different parties are in power. Building on this assumption, the project will assess (1) how parties coordinate internally, (2) how this reflects on the behaviour of parliaments, and (3) how this affects the relations between parliaments and governments across governance levels. Overall, the project aims to shed light on the broader functioning of modern democracies. The project will compare three cases of federal-type systems: Belgium, the US and the EU; as these cases represent not only different types of multi-level systems, but also different types of democratic systems. The project aims to develop long-term data by using the process tracing method. The author hopes that presenting this project at the Graduate Conference will result in delivering useful feedback for the further development of the research design.