The cognitive linguistics literature on metonymy has brought to our attention the central role played by this phenomenon hi conceptual processes; however, we believe that no clear dividing line has been drawn to distinguish it from metaphor. We analyse some of the existing proposals and argue for a treatment of metonymy in terms of three parameters: domain inclusion, domain expansion and reduction, and domain highlighting. In this connection, we postulate the existence of two basic types of metonymy, source-in-target and target-in-source, each of which exploits the aforementioned parameters in a different way. We further argue that an understanding of the cognitive operations involved in each of these two metonymic types is crucial in order to identify the different interactional choices which make use of metonymy. We also examine other complementary interactional patterns based on image schemas and on propositional idealised cognitive models. We finally observe that interactional choices predetermine to a large extent the nature of much of our inferential activity. (Francisco José Ruiz de Mendoza Ibáñez and Olga Isabel Diez Velasco)