This thesis explores why political elites in post-conflict ethnically divided states accommodate or resist each other across ethnic lines. The geographic focus of research is on post-conflict Bosnia and Herzegovina, and Macedonia. In both countries the track record of post-conflict politics has been uneven and on some issues political elites still resist agreement and co-operation across ethnic lines. This thesis explores the reasons behind this mixed pattern of ethnic accommodation and resistance. Based on the post-conflict literature in social science, the thesis examines the impact that the following explanatory variables have on ethnic accommodation and resistance: power-sharing mechanisms, political party dynamics, informal practices, policy legacies, and external actors. The analysis is situated at the policy level. Two policy areas, highly sensitive for ethnic relations in the post-conflict context, are analysed and compared in each of the two countries. In Bosnia, the focus is on military and police reforms; in Macedonia, on minority education and decentralisation. Within the wider institutionalist approach, the empirical chapters present the findings of process tracing in each of the four policy fields. Based on these findings, the thesis demonstrates that although power sharing arrangements tend to lead to greater ethnic accommodation, they are not always sufficient to produce accommodating outcomes. Informal practices often supplement the work of formal institutions in providing incentives and means towards greater accommodation. External actors tend to enable greater accommodation when perceived as neutral and credible by domestic political elites. Ethnic divisions in both countries remain and require regular management by a flexible set of institutions, which can accommodate challenges unforeseen by peace agreements.