This chapter presents the conceptual framework of the book that builds upon several strands of literature: socio-technical systems, institutional and political change, and securitisation. Drawn from existing literature the authors argue that several key factors account for national climate and energy policies, and explain the extent of the region’s climate and energy policy homogeneity and heterogeneity. Such an approach enables the book to identify the differences between individual CEE countries – for instance, the role of ideas can be used to describe the different understandings of what constitutes energy security issues, and the solutions to these. Some but certainly not all countries in the region securitise this issue (e.g., Lithuania and Poland) and frame energy security as a national security challenge, highlighting the foreign policy implications of climate and energy policy and influencing both domestic and EU policy choices.