The study examines how social media can be used in a business-to-business context. To understand the communication conditions, factors has been identified that affects the choice of communication channels for different types of information transferred between parts. Furthermore, the study investigates the underlying reasons for why certain communication channels are chosen before others, in different situations. The study results are based on qualitative semi-structured interviews with employees in a small engineering consulting company. The investigation has focused on employee communication and choice of communication tools primarily in relation to the business relationship. The study answers the following questions: What factors may contribute to the selection of different communication tools in business-to-business? What are the conditions and reasons for employees to use social media in business-to-business? What opportunities can social media pose for managing knowledge exchange with customers in business-to-business? The theoretical framework is based on Media Richness Theory and Social Influence Theory. The results show that factors that affect use of social media between businesses are 1) social environmental influences on attitudes towards social media (positive or negative), 2) individual analogue and digital values, 3) social media are primarily used in a private context 4) individual's role and level within the company. It is proposed that companies require strategies and increased knowledge to operate efficiently with social media in business to business. The results also shows that factors affecting the choice of communications channels between employees and business relationship are: 1) context-dependent, 2) the availability and accessibility, 3) the role and level in the company, 4) customer relationship development, 5) the information degree of ambiguity, 6) communication channel degree of "richness", 7) urgency, 8) confirmation of agreement.