The recent resurgence of growth studies has clearly established that technological progress and knowledge accumulation are among the most important factors in determining the performance of regional and national economic systems. Nonetheless, few empirical studies have tried to analyse the flows of technology and knowledge across regional economies in Europe due to the lack of adequate indicators. In this paper we propose new evidence on the characteristics of knowledge flows across European regions based on a statistical databank, set up by CRENoS, on regional patenting and citations at the European Patent Office spanning from 1978 to 2004 and classified by ISIC sectors (3 digit). We consider 175 regions of 17 countries in Europe assigning each patent a region according to the place of residence of the inventors; then, we examine in- and out-flows of patent citations as a proxy of knowledge connections, while looking also at their sectoral differences and dynamics through time. The econometric analysis is based on a model where the transmission and exchange of knowledge across regions is mainly affected by geographical distance together with a set of spatial dummy variables. Moreover, we make several controls to check for the robustness of our results with respect to the inclusion of other characteristics of the origin and destination regions (production structure, economic conditions and technological efforts) as well as different estimation methods. The main result is that knowledge flows decrease as the geographical distance between the origin and the destination region increase. Furthermore, knowledge flows tend to be higher among contiguous regions and areas within the same country.