The development of publication activity and citation impact in Scandinavian countries is studied for the 1980-1997 period. Besides the analysis of trends in publication and citation patterns and of national publication profiles, an attempt is made to find statistical evidences of the relation between international co-authorship and both research profile and citation impact in the Nordic countries. A coherent Scandinavian cluster has been found, and the Nordic countries have strong co-authorship links with highly developed countries in West Europe and North America. It was found that international co-authorship, in general, results in publications with higher citation rates than purely domestic papers. International collaboration has, however, not the same influence on publication profiles and citation impact of each analysed countries.