We investigate the degree of financial integration within and between European countries. We construct two measures of de-facto integration across European regions to capture “diversification” and “development” finance in the language of Obstfeld and Taylor (2004). We find evidence that capital market integration within the EU is less than what is implied by theoretical benchmarks and also less than what is found for U.S. states. We ask why is this the case? Using country-level data for economic institutions, we find that these are not able to explain differences between countries.