The September 11 attacks employed violence as a means of picture-making on a horrifically unprecedented scale. Furthermore, ‘9/11' crystallised the intersection of trauma discourse and visual culture at both popular and academic levels. Questions surrounding the role of visual images and processes of mediation within trauma theory are thus important in understanding an event which was fundamentally mediated and intensely visual. The concept of ‘virtual trauma' raises the possibility that mediation can become the site or source of trauma, as well as a mode of its transmission or representation. This thesis explores the ways in which the confusion of presence and absence named by the figure of virtuality operates in the register of visuality and visibility, both literal and figurative, in specific representations of 9/11 by Don DeLillo, Frédéric Beigbeder, Paul Greengrass and Luc Tuymans. These are read as responses to the problem of how to represent an event which was already its own representation. It therefore seeks to situate 9/11 within a history of technics as the enframing of a particular relationship between subject and object through representation, as proposed by Heidegger and developed by others including Derrida and Samuel Weber. Through detailed analyses of these works and their popular and academic reception, I highlight the ways in which they both employ and problematise structures of visibility, presence and mediation. Such representations offer an account of the tension between securing and ‘unsecuring' of the subject or beholder which is, in Weber's reading of Heidegger, the result of representational thinking. The thesis thus moves discussion of the impact of 9/11 into the wider context of debates over visuality and subjectification in contemporary media cultures.