This work attempts to provide a methodology to characterize cooperation links within a network of SME's. The proposed methodology permits to identify potential ties between firms within a network. It is based on theoretical approach taking in account structural characteristics of firms, such as complementarity of activities and similarity of competencies. Two organizational maps are plotted, a map of potential coordination modes and a map of actual coordination modes. The comparison of the two maps permits to identify some of other parameters influencing cooperation between two firms.