Abstract. This paper analyses relationships between university research performance and concentration of university research. Using the number of publications and their citation impact extracted from Scopus as proxies of research activity and research performance, respectively, it examines at a national level for 40 major countries the distribution of published research articles among its universities, and at an institutional level for a global set of 1500 universities the distribution of papers among 16 main subject fields.

Both at a national and an institutional level it was found that a larger publication output is associated with a higher citation impact. If one conceives the number of publications as a measure of concentration, this outcome indicates that, in university research, concentration and performance are positively related, although the underlying causal relationships are complex. But a regression analysis found no evidence that more concentration of research among a country's universities or among an institution's main fields is associated with better overall performance.

The study reveals a tendency that the research in a particular subject field conducted in universities specializing in other fields outperforms the work in that field in institutions specializing in that field. This outcome may reflect that it is multi-disciplinary research that is the most promising and visible at the international research front, and that this type of research tends to develop better in universities specializing in a particular domain and expanding their capabilities in that domain towards other fields.