This study is mapping the most significant challenges and obstacles for a reinforced Nordic cooperation on data resources. Focus is put on existing national databases and registers established mainly for administrative purposes but also the question of newly-generated scientific data is handled. The challenges are analyzed from political, legal, ethical, organisational, technical and financial perspectives. The broad scope targets primarily policy makers involved in eScience development on national and/or Nordic level. Involved parties in the study are Nordic Council of Ministers, NordForsk, Finnish Ministry of Education and Culture and CSC - IT Center for Science. Special focus has been put on the challenges for register-based research, since all the Nordic countries have a vast amount of population-based registers which are considered not to be used to their full potential in various research fields. One of the challenges is to find way to combine these registers with other research data and the Nordic countries have to find their own way of unique collaboration methods, since there are no equivalent pre-conditions for this kind of research in the rest of Europe. The study also gives a national overview of the current progress in the five Nordic countries, to raise awareness of important national initiatives which can contribute to a stronger collaboration on the Nordic level.