The paper aims to investigate the role of purchasing and marketing in collaborative product development when they involve suppliers and customers. Six collaborative development product development projects at different large high-tech firms are studied. The results show that purchasing and marketing differ in regard to their contributions and roles of managing partner relationships. Purchasing appears to collaborate more with R&D and have well-established routines, processes and strategies for handling both technical and relational issues with suppliers. Marketing, on the other hand collaborate less with R&D and have fewer routines, processes and strategies for managing customers involved in product development.