The article analyses ethnonational conflicts in Belgium and Canada during the period 1960-1989. Using the most similar case design, it is argued that the different policy performances in Belgium and Canada can be accounted for by the institutional context in which the conflicts occurred. The institutional setup in Canada and Belgium created different modes of joint decision making. Through an analysis of three joint decision variables, namely, decision rules, preferences and default conditions, two empirical cases are scrutinized. The Canadian Pension Plan in Canada and the institutional reform efforts in Belgium (1974-1977) highlight the importance of institutional default conditions. On the basis of these empirical cases it is argued that the different conditions of joint decision making in the two states lead to a continuous production of compromises in Belgium and a genuine absence of mutual agreement in Canada.