There are major change factors affecting to operational environment of purchasing and supply management. Global supply market is opening up for all size of firms, servitization as product strategy is changing what is delivered and technological advancement enables digitalization changing the business processes. Volume of available information increases making external knowledge acquisition a core competence. Under this immense change, it is important for purchasing and supply management to understand, how can they efficiently connect requirements of own production to supplier capabilities and develop those together in order to match customer needs. 
Knowledge acquisition constitutes a continuous learning process. During learning routines, actions and division of labour are reformulated, recombined and finally institutionalised to construct new operational environment – new social reality. Learned new skills and acquired new knowledge shape the environment requiring continuous learning. Given the expansive cycle nature of learning, knowledge is interesting resource – more it is used, more it increases. 
In the thesis, qualitative and quantitative research methods are used to study the impact of the supply network change to purchasing and supply management. The phenomena is looked from small and medium sized enterprises point of view. Purchasing management in small and medium sized firms is in contradictory position in stringent competition, when innovation capability and time-to-market are gaining more and more importance. In spite of being more flexible than large, they are constrained by limited resources to implement new practices in to the use. As organization they have lower capacity to absorb external knowledge and maintain own learning capability at required volume. At the same time and for the same reasons their performance development depends increasingly on external knowledge. 
The thesis attempts to answer two questions. First, what is the impact of described changes of supply network on purchasing in terms of information-processing requirements? Second, what impact do the changing supply network trends have on information-processing capabilities in purchasing? 
The thesis contributes to discussion of purchasing and supply management. It builds on theories of resource-based view and knowledge-based view of a firm. Applying abductive research approach the thesis provides new understanding on role of purchasing and supply management in knowledge acquisition and use of organizational learning to develop buyer-supplier relationship. 
First, the purchasing management has to manage contracts and coded knowledge in order to obtain reliability, quality and performance. However, purchasing must bring in new knowledge and skills to organization beyond what has been stipulated in contracts. For example in project deliveries, products are developed and defined during the delivery requiring flexibility in purchasing. 
Second, in the thesis purchasing is observed from service logic point of view. Service logic has been instrumental in marketing emphasizing process how value is delivered instead of product itself. In purchasing, the service logic turns the focus from contact-controlled transactions towards continuous development of skills and knowledge with suppliers. 
Third contribution of the thesis is in bringing the organizational learning to purchasing and supply management discussion. In the thesis, different learning orientations are matched against different operational strategies and compared with expectations on buyer-supplier relationships. 
Fourth contribution is in building a path from knowledge acquisition through different organizational learning orientations to purchasing performance. It is demonstrated how purchasing uses different supplier development and knowledge acquisition methods and what is effect of those to purchasing performance. 
As management implications, the thesis provides constructive methods to assess what new purchasing capabilities are needed and how they should be developed in accordance with overall strategy development. The thesis sheds light on changes on purchasing when firm expands to new supply markets and when market shifts towards service logic. The purchasing has to be able exploit current knowledge and explore new processes and practices with existing suppliers but also have capacity to explore new supply market more proactively.