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. In this paper we propose new evidence on knowledge flows across European regions based on patenting at the European Patent Office. We examine in- and out-flows of patent citations as a proxy of knowledge connections, while looking also at their dynamics through time. The econometric analysis is based on a model where the exchange of knowledge across regions is mainly affected by geographical distance together with a set of spatial variables.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. These results prove to be robust 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.