The interest of the study of secession processes and its consequences in the international relations arena motivated this research launched by CIDOB in collaboration with CEPS, ISIS and ICCS, amidst the recent events that surfaced in Scotland, Catalonia and others towards independence. To date, none of the European Union countries have experienced a break-up of a part of its territory once they have joined the EU. 2014 marked a referendum in Scotland and massive citizen mobilisations in Catalonia on the independence question. In Scotland, the referendum, despite tight results, was in favour of rejecting secession. In Catalonia, as the independence alternative is gaining ground while political and legal quarrel between the national and regional governments continue, a full-fledged and informed economic assessment of the different scenarios is needed to devise the best policy options for future developments.