The identification and selection of a suitable partner is an important condition not only in formation, but also for stability of the cooperative agreements. This article intends to show precisely the interest of identifying and selecting potential partners in a cooperative agreement. Therefore, to reach this goal, some results from an empirical study based on a sample of 114 cooperative agreements formed by Portuguese firms are presented. The results show that the criteria for selecting a partner in cooperative agreements are categorised in four dimensions: 1) reputation and contribution of resources; 2) complementarity and personality of the entrepreneur; 3) organisational culture; 4) local/regional identity. These dimensions are associated both with firms' resources and capacities, and with the characteristics that define the personality of entrepreneur. Implications for theory and practice are also discussed.