An unprecedented process of financial consolidation has taken place in the European Union over the past decade. Building on earlier US evidence, we examine the impact of strategic similarities between bidders and targets on post-merger financial performance. We find that, on average, bank mergers in the European Union resulted in improved return on capital. By making the assumption that balance-sheet resource allocation is indicative of the strategic focus of banks, we also find significantly different results for domestic and cross-border mergers. For domestic deals, it could be quite costly to integrate dissimilar institutions in terms of their loan, earnings, cost, deposits and size strategies. For cross-border mergers and acquisitions (M&As), differences of merging partners in their loan and credit risk strategies are conducive to a higher performance whereas diversity in their capital, cost structure as well as technology and innovation investments strategies are counterproductive from a performance standpoint.