In this paper we examine how the figure of the teenager is positioned within the discourses and practices of commercial online media. In particular, we explore how the popular, Australia-based web portal "ninemsn" works discursively to shape the identities of young people. Ninemsn not only constructs and circulates selected representations of teenage media users, but also makes available to them particular kinds of texts and communication practices. At the same time it pursues its own commercial agenda, which aims to attract and expand particular audience segments and niche markets and sell them on to advertisers for a range of media forms and products. Ninemsn's development of "personas" to aid the processes of site design and marketing is especially notable as an attempt to more precisely outline particular subject positions for users and offer detailed representations of imagined consumers to advertisers. (Contains 2 notes and 2 figures.)