The paper introduces a formalisation of opportunities, as situations that can be exploited obtaining valuable outcomes, in the context of the social networks, and defines a methodology for discovering opportunities through the analysis of the relation among network actors. The proposed methodology is then applied to the research-oriented networks, whose members share paper coauthorship or potential research interests. Finally, its validity is tested by evaluating the research collaborations opportunities exploited in the context of two distinct research communities, modelled through the analysis of their publications over time.