eng: More and more media companies use the Internet. Thus is this new information- and communication technology a new field of media economics. The dissertation gives a short overview over media economics and the Internet and the main economic aspects. These are the changes (a) of the value chains in different media sectors, (b) for companies and media markets (costs, revenues, concentration etc.) and (c) for media marketing. Details from an empirical study about austrian bookshops (content analysis of the websites and questionaire) complement the theory.