In this paper we investigate the determinants of cooperative innovation and put our main focus on the regional or spatial and on the technological or sectoral dimension. We suggest a method to disentangle these two factors and to extract differential regional effects. The latter can be used to identify and evaluate the strength of regional innovation systems. Applying this method to German patent data we find evidence that regional differences in the degree of cooperative innovation are not only due to the technological/sectoral composition of the region but also due to a specific regional effect.