| The business model of tourist sites has evolved and the information and communication technologies tools have become a cornerstone of the current model, where companies, and users or tourists converge. In this scenario, the web plays a crucial role: through it, third party observations and ratings become an element that generates a degree of influence that affects the decision of users of tourist sites. This study aims to determine precisely the degree of impact of the independent variables -number of observations and ratings by third parties- on elements or dependent variables, such as attention to the site, information and probability of booking, all mediated by the concept of susceptibility or impact of the perception of the influence of third parties. The methodological process implemented includes an initial exploratory sampling to determine and validate the levels of the independent variables and the design of the tourism offers, in addition to convenience sampling and the use of a factorial model of experiment design. It is concluded that the volume of observations issued by third parties, as well as the evaluations it reflects, constitutes a preponderant factor when deciding on a tourist site, and that the role of susceptibility directly affects the user's needs in terms of information requirements, attention, and influences the probability of booking the tourist site.