Pornography addiction has seemingly become a quintessential explanatory resource for describing the problems of pornography. Yet, while the presumed inability of pornography viewers to correctly moderate their viewing is central to the pornography addiction concept, the shear variety of proposed outcomes of viewing ‘too much’ pornography, or viewing the ‘wrong kind’ of pornography, suggest the operation of a much more nebulous concept. Drawing on empirical interview data with self-described pornography addicts, this chapter explores the ways that a diagnosis of pornography addiction depends upon an ambiguous and poorly defined concept of boundary crossing. Indeed, the concept of threshold as it relates to pornography addiction forces us to ask questions as to how pornography viewers make sense of the difference between ostensibly ‘normal’ (and to a degree normative) and ‘addictive’ pornography viewing worthy of diagnosis.