Understanding why indecent images of children are produced and collected involves issues beyond the legal definition of child pornography. An over-emphasis on a legal approach will not necessarily assist in the development of preventative and control strategies. This article provides a brief overview of the way in which the Internet can be misused for sexual gratification and has identified some of the issues that seem to be significant in understanding the nature and dimensions of Internet sexual offending. The main descriptive typologies that underpin research relating to Internet child sex offenders have been reviewed and critically evaluated. As discussed throughout this article, one of the most challenging issues continues to be the difficulty in placing Internet sex offenders into categories. The foregoing discussion indicates that Internet sex offenders comprise a heterogeneous population and that there appears to be a lack of a coherent and agreed framework for defining their activity. (Published Abstract)