Productivity across European regions is related to three types of networks that mediate R&D-related knowledge spillovers: trade, co-patenting and physical proximity. Our panel estimations for European regions suggest that all types are important vis-à-vis each other but that local productivity gains in innovative followers or lagging regions that link up to innovative leader regions are conditional on human capital and absorptive capacity. Without these capacities, regions are left unaffected by network externalities and knowledge spillovers, and knowledge and productivity may instead boil down only in leading regions. This may frustrate recent European policy initiatives, such as the Open Research Area and Smart Specialization, that are designed to benefit all regions in Europe.