ABSTRACTThe main focus of this paper is the relationship between export diversification and export performance. The key difference with respect to the previous literature is that export diversification is measured and related to export volume by destination country. The approach is empirical and an aggregate export demand setting is adopted to test the significance and influence of export diversification, measured via the Herfindahl index, on export performance by destination country. The econometric estimation is performed using export data for Spain to its partner countries for the period 1999–2011. The main finding is the positive relationship between Spanish export concentration and export performance by destination market. This finding is shown to be robust to several econometric specifications.