This research extends Hoffman et al (2010)'s work on the relationship between two key targets for co-creation: Emergent-Nature Consumers (ENC) and Lead-Users (LU). These authors have shown that an ENC - who can innovate in any domain, could be more effective than a LU- who innovates in one specific-domain, for the development of new product concepts. We show that these two innovating users have common conceptual roots and that ENC character trait corresponds to an extension of LU characteristics to all product domains. We also show that the ENC trait is an antecedent of specific-domain lead-usership. It finally appears that ENC and LU characteristics are crucial determinants for engagement in co-creation activities.