This thesis has two main aims, investigated in three research questions. The first aim is toinvestigate first how hospital professionals, like secretaries’, nurses’, and doctors’, knowledges isaccomplished, used and distributed within the professional network, and secondly howinformation technology is used in these knowledge processes. The second aim is to look into howpatients and parents interests are taken into account when performing treatment. The setting is theexpert hospital Rikshospitalet, and the department of neurosurgery. An interpretive approach wasused where interactions between hospital professionals, patients and parents were observed, andinterviews performed later. The analysis is performed using aspects from knowledge theories likeknowledge in practice, communities of practice, the difference between scientific and layknowledge, as well as philosophical-historical elements related to the clinic. These aspects areanalyzed using the theoretical framework of Actor-Network Theory (ANT). ANT enables anunderstanding of the treatment process as a network of action across different communities. Thetreatment is a relational process where different actors with different knowledges meet in order toattach necessary resources and perform treatment. The process is about obtaining partialalignment by taking into account different types of knowledges. If the doctor, and otherclinicians, is able to see and understand the patient’s interests, and take them into account, it mayimprove treatment processes. Three different aspects are analyzed. First, the structure of successin the treatment process relates to the ability that the doctor has to switch between differentontological perspectives. If he is able to understand and integrate the patients’ interests, theenrolment succeeds. A second aspect regards what happens when the enrolment strategy fails,and suggests that this can happen because the professionals are not able to integrate knowledgeperspectives in addition to the ones revealed by their technological apparatus (the medical gaze).The third focus is about how the increased amount of knowledge challenges the experts and theirdecisions. It is very difficult to identify new knowledge because it is continually created. Thiscreates situations where experts make choices, but where patients can locate experts elsewherewho can do better. The thesis gives contributions to the area of health informatics and knowledgemanagement. First it enables an understanding the knowledge used in treatment processes, andthe challenges and problems different types of knowledge may lead two. Secondly it providesinsight into aspects of lay knowledge amongst patients, and what information lay people use inorder to secure their interests.