The aim of this research was to explore the user participation behaviours in the emerging structure of organisational social media platforms; a term coined and defined in this thesis. This emerging community structure originates from technical discussion forums and knowledge repository systems, and appears to be concerned with solving user problems, generating professional and technical content, and facilitating interaction in the external organisational domain. This research has explored three such platforms in the software and technology sector; namely, the SAP Community Network, the Oracle Community site, and Microsoft's professional platforms, MSDN and TechNet. Qualitative open-ended interviews were conducted and analysed under the interpretive paradigm, to generate a theoretically-grounded account on the use of social media tools in this context, the benefits and value outcomes gained, the underlined reasons and motivations that drive participation, and the emerging impact of active contribution as external users gain recognition. It was found that organisational social media platforms enable the development of rich technical content, personalised experience and thought leadership, creating in this way an environment for problem solving, professional development and expert recognition. The voluntary participation observed is evidently underlined with a combination of altruistic attitudes (e.g. satisfaction, enjoyment and a pro-sharing attitude), reciprocal helping behaviours (e.g. paying it forward, and sharing knowledge and experience) and personal gain expectations (e.g. visibility, recognition and career advancement). The individual platform users appear to acquire participation roles based on their technical expertise (newbie, knowledgeable and expert) and on the level of engagement they wish to undertake (lurker, contributor, community influencer and recognised user). A group of highly active users is formed in this way at the top tier of participation that establishes channels for professional credibility, product feedback and external advocacy through a close relationship with organisational members. These findings suggest that organisational social media platforms can constitute a new interface with the external environment and a potential business model, under which flexible forms of communication and interaction affect the support infrastructure changing the way in which customer service can be delivered, product and sales advocacy can be established, and innovation and product development can be achieved; complementing in this way internal processes with external activity.