Due to expected benefits such as citizen participation and innovation, the release of Public Sector Information is getting increased attention on various levels of government. However, currently, data release by governments is still novel, with little experience and knowledge thus far about the benefits and barriers of release. This is compounded by a lack of understanding about how internal processes influence data release. Our aim in this paper is to get a better understanding of these processes and how they influence data release, i.e, to find determinants for the release of public sector information. For this purpose, we conducted workshops, interviews, questionnaires and desk research. We find that the way data is used by a department, the way data is obtained, how data is stored, and the suitability of data to become open, as crucial indicators for open data release. We conclude with lessons learned based on the research findings. These are that we should take a nuanced approach towards data release, avoid releasing data for it’s own sake and take small incremental steps to explore data release.