Once a year for over forty years public relations’ practitioners in Sweden gathers, the political week in Almedalen, in the town of Visby. There they exchange knowledge and experience on all types of subjects using different and common communication models whether they are aware of them or not. The research on communication models is sparse, with one exception: Grunig’s model. Both practitioners and researches believe them to be important, even strategic. But too little knowledge about the models as such negatively impacts the understanding of public relations’ activities. It also contributes to the view that public relations is frittered. The thesis studies and analyses communication models of public relations. Models have been created by theorists and practitioners to describe the phenomenon, to understand communication as such and to facilitate communication between humans. The thesis addresses basic questions such as which models there are, where they stem from, who the originators were and the characteristics of each respective model. The basis of the study is comprehensive Anglo-American literature. All in all, over twenty different models have been analyzed in three different ways, i.e. the structure of a model, its historical deposits (sediment) and the application of the model. The result is manifold, since many characteristics form ten attributes and three families of models (a reduction). The characteristics can be seen as the models’ building blocks, e.g. the direction of the communication, the number of contacts and synchronism. Three model families are built on three differentiating characteristics, and the families are named correspondingly. Directional model (Riktningsmodellen), the Co-orientational model (Saminriktningsmodellen) and the Connectivity model (Konnektivitetsmodellen). The classification is of course not set in stone. It should be regarded as a first step to reduce the number of models in use and concentrate on the important characteristics of the models that help public relations researchers and professionals to solve problems and theorists to explain, foresee or guide to better public relations. Finally, five areas of future research are presented: a multinational study of models, a study of practitioners’ model use, a deeper history study according the concept of sediment, a notational system for models and, last but not least, a development of the Connectivity model. The last subject is the one that once inspired me to write a thesis. / <p>QC 20170426</p>