[en] This PhD thesis focuses on the impact of the European Union Emissions Trading Scheme (EU ETS) on investment decisions in the European power sector. We provide the policy background on the EU ETS and contemporary policy and economic developments. We discuss the main types of compliance buyers' responses to the EU ETS constraint: emissions reductions, acquisitions of additional compliance assets, and other responses. We present the results of an empirical survey of the most carbon constrained European utilities. We show that strategic and economic considerations prevailed over the introduction of the carbon price. We discuss the impact of those investments on European utilities' EU ETS profile by looking at the potentially locked-in emissions, changes in the compliance perimeter and some specific developments relative to carbon leakage and Kyoto offsets. We offer a review of the investment decision-making approaches. Exploring the impact of carbon price scenarios on generation investment portfolios, we are able to identify that: the EU ETS has a moderate but central reallocation role in power generation investment portfolios; insights into the long-term carbon price trend are particularly helpful to unlock investment; some much discussed policy provisions only have a relatively small impact on investment portfolios; carbon price expectations impact decisions relative to power generation investment portfolios; while the EU ETS has a central role, the climate and non-climate policy mix matters most. (author)