We examine the relative benefits of industrial versus geographical diversification in the Euro zone before and after the introduction of the common currency. A priori, one may expect that increased stock market correlation would precipitate a move from geographical towards industrial diversification. We employ the empirical model of Heston and Rouwenhorst but show that adopting a panel data approach is a more efficient estimation method. We find evidence of a shift in factor importance; from country to industry. However, this is not exclusive to the Euro zone but is also present for non-EMU European countries. Therefore, fund managers should pursue industrial rather than geographical diversification strategies. (C) 2004 Elsevier Ltd. All rights reserved.