Why do states voluntarily pursue cooperation? This chapter looks into the national preferences of the Black Sea states in joining subregional schemes. There are a variety of reasons – conflicting or complementary – that are put forward, making the identification of a common determinant not realistic. There exist complementarities of interests and concerns but not a single, common motivation among all partners. National preferences and their interplay shape cooperation dynamics. The term ‘preference’ rather than ‘interest’ is used here in order to indicate that state behaviour is not permanent and ‘fixed’ as in the realist approach, but it changes over time, reflecting domestic parameters and social processes. State preferences do not remain constant and unchanged, nevertheless some aspects of national interests display resilience and span over time. The fixed interest is useful in a given time span when and where the state preference is unchanged. Here, what it is examined is the basic features of national preferences of Black Sea states over subregional cooperation since the early 1990s. Emphasis is placed on the initial stages of the formation of BSEC and its later evolution. Given the systemic changes in the post-Cold War Black Sea area and the emergence of new state entities, national interests and priorities let alone regional ones clearly defined for the majority of Black Sea states were absent. Most of the countries concerned were newcomers in the international system, being preoccupied with the existential urge of building national institutions and gaining international recognition. Domestically rooted interests, as well as domestic interest groups, were not consolidated yet either but played a role in shaping foreign policy.