Dairy production has long been the most important production line in Finnish and Norwegian agriculture. Prior to Finland joining the EU, farm structure as well as national agricultural policy was very similar in the two countries. In this paper, we explore development and differences in productivity and efficiency trends in the two countries before and after 1994 when Finland joined the EU. The challenge is to isolate the effect of EU-membership from other events like introduction of milk quotas, and more generally, changes in agricultural policy and macro-economic factors. We model productivity growth by means of standard production efficiency frontier models on twenty-year panels of Finnish and Norwegian farm accounts data.