This paper focuses on the role of inter-organizational networks as facilitators of knowledge flow and innovation. It introduces the concepts of network capital and network space to complement existing notions of social capital and geographic space as explanatory factors underpinning the impact of networks. Empirically, the paper analyses the inter-organizational networks of firms across three different regional settings. As well as finding significant differences across regions, the analysis also finds cross-regional commonalities in terms of the association between the innovation prowess of firms and the nature of their networks. In particular, it is found that the innovation performance of firms is significantly related to network capital investment in dynamically configured inter-organizational knowledge alliances. It is concluded that such findings may provide clues in terms of policy making in areas such as cluster and innovation system development, especially in supporting and orchestrating networks which have a clear strategic and calculative rationale.