The creation of sustainable cities is believed to solve all our urban problems, whether the problems are environmentally, socially or economically. ‘Sustainable cities’ have gained widespread scientific and political consensus, and organisations such as the United Nations, the European Union, NGOs and other political agencies have worked out concepts and plans for the development and implementation of it. These plans are manifested in reports and other policy documents that address decision-makers and the general public to follow suggestions for action. Central features in these plans are how sustainable cities are to be understood, what sort of problems cities face and how to cope with these. In particularly, city planning and technology have a crucial role to play in the achievement of sustainable cities. This thesis seeks to investigate whether the idea and the conceptualisation of the sustainable city is presented different by different agencies. Here, why similarities and differences exist are to be explained and accounted for. Furthermore, a special focus is put upon how city planning and technology are to solve urban problems, and whether these solutions and the idea of the sustainable city vary between different documents represented by agencies on different geographic scales. In order to address the scale issue, three documents are selected for closer investigation: the Habitat Agenda 2 of the United nations, the Sustainable Cities Report of the European Union, and Creating a Sustainable London, written by London Sustainable Trust.Analysing the sustainable city as represented by different agencies pose questions with regard to the method that is to be applied. The method applied in this thesis, is a discourse analysis of these documents within the framework of actor-network theory. According to this theory, texts (actants) can make it possible for the authors (actors) to achieve power. Furthermore, the texts can function as instruments to build up and stabilise networks in order to strengthen and stabilise theories and ideas.It is argued that the idea of the sustainable city is presented in such a way that it is impossible to resist. This is made possible by work of the authors who mobilise scientific articles, political conferences and other entities to support their claims. Furthermore, the ‘sustainable city’ functions a symbolic umbrella; hence actors with often contradicting interests can support the idea. The ‘sustainable city’ thus becomes an adaptive concept that is used by many actors, on different geographic scales. These scales are also produced and reproduced by the work done by actors in heterogeneous networks.For city planning, it is found that empowerment, bottom-up and participatory planning are emphasised together with the importance of experts and scientific planners, who are to manage the urban environment. Here we see that modern and post-modern concepts on planning and development are used in chorus. As for technology, we face a technological paradox: the authors of the document point out sustainable technologies as main instruments of creating sustainable cities while at the same time identifying environmentally adverse technologies as the main cause of unsustainable cities.