Finding proper policy instruments to promote productivity growth features prominently in the Europe 2020 strategy and is central in many national as well as European policy debates. In view of the increased mobility of high-skilled workers in Europe, ongoing globalization and increased interregional and international co-operation, location patterns of innovative activity may be subject to drastic changes. A proper understanding of location patterns of innovative outputs can enhance the effectiveness and efficiency of national and European placed-based innovation policies. Building on the literature on the knowledge production function, the aim of this article is to explain the observed differences in the production of innovative outputs across European regions. Our main research question is whether geographical proximity and social capital are important vehicles of knowledge transmission in Europe. Several other variables are used to control for structural differences across European regions. We find support for the hypothesis that both social capital and geographical proximity are important factors in explaining the observed differences in the production of innovative output across European regions.