The advent of the internet has added another medium in which people can engage in sexual behaviour. This ranges from the passive consumption of online pornography to the interactive exchange of sexual content in cybersex chat rooms. It is believed that access, affordability and anonymity are critical factors that make the Internet viable for the acquisition, development and maintenance of online sexuality. For some, sexual behaviours online are fulfilling, whereas for others, they may take on addictive qualities. Internet sex addiction can be conceptualized as the intersection between Internet addiction and sex addiction and the current literature suggests that there does not appear a clear dividing line between these psychopathologies. The aim of this paper was to provide a comprehensive overview of the empirical studies that have investigated Internet sex addiction in adults. Based on these, it was concluded that engaging in sexual behaviours on the Internet can go awry and result in Internet sex addiction, as it can lead to a wide variety of negative consequences for the individuals affected. Particular attention is drawn to the implications for future research in order to establish the pathological status of Internet sex addiction as a sub-form of Internet addiction, that shares characteristics of real life sex addiction, but which is not to be equated with it. Accordingly, the need for a clear diagnostic framework to clinically assess Internet sex addiction is emphasized as the first step towards understanding the potentially psychopathological qualities and repercussions of sexual behaviours on the Internet.