This thesis is concerned with the development of digital governance. The main goal of the thesis is to analyse and explain patterns and levels of digital governance through the lens of actorcentred institutionalism and institutional change. More concretely, the research question of this thesis is: “To what extent do changes in institutional arrangements, organisational processes, and actors’ preferences influence changing patterns and levels of digital governance over time and across space?” To answer this question, this study employs a multi-method approach, combining statistical analysis and case study research. The quantitative part of the thesis consists of time-series cross-sectional analysis of forty-one countries over the period of 2003- 2016. The qualitative part includes two in-depth case-studies, Estonia and the USA, and traces the development of digital governance from the early 1990s onward. One of the main findings of this study is that the level of digital governance is largely determined by institutional factors. This finding is supported both by the statistical and the qualitative analyses of the thesis. However, the findings of the in-depth case studies also suggest that the effect of institutional arrangements may vary across countries over time as it has been consistently stronger in the USA than in Estonia, and it has been increasing over time in Estonia. I find modest support to the hypothesis that organisational processes affect the level of digital governance. Regarding the role of actors, the results are not clear-cut, and they are rather surprising. The statistical analysis reveals that digital governance is negatively affected by politicians’ preferences but positively influenced by the private sector whereas the public has no effect. The qualitative study partly confirms these findings, indicating that politicians play a minor direct role in the development of digital governance. Instead, progress in this area has been mainly in the hands of government officials, which have been supported both by the IT sector and favourable legislative frameworks. Overall, this study suggests that digital governance has not been, until 2016, a politicised issue, and this has created good conditions for government officials to take the lead in the development of digital governance.