In some large European countries, in recent decades, economic globalization has gone hand in hand with a powerful trend to political decentralization (this has been the case in the United Kingdom, France, Italy, and Spain). In Spain, and after years of apparent stability, the relations between Catalonia and Spain are experiencing troubled times. This paper examines particularly the main economic effects of both the staying together and the secession scenarios. Following the introduction, the second section reviews some aspects of the relations between Catalonia and Spain. The third and fourth sections analyse different scenarios with a particular focus on the main issues that the secession scenario raises. The fifth section contains a concluding remark.