Are knowledge flows all alike? Evidence from European regions. Regional Studies. The paper investigates the impact of distance, contiguity and technological proximity on cross-regional knowledge flows by comparing the evidence concerning co-inventorship, applicant–inventor relationships and citation flows. Evidence is found of significant differences across these diverse kinds of knowledge flows for what concerns the role of distance, and the moderating role of contiguity and technological proximity. Moreover, it is shown that border effects may prove crucial in a twofold sense. On the one hand, contiguity between regions belonging to two different countries still plays a moderating role, although weaker as compared with that of within-country contiguity. On the other hand, regions sharing a frontier with a foreign country are more likely to exchange knowledge with this foreign country than other regions which are far from the border.