This study aimed at understanding the factors that influence the purchase intention and the positive word-of-mouth of online booking sites. The purpose was to understand the reasons that lead people to use and recommend this type of service in the internet, even though the online media approached tourism consumers from their suppliers, such as hotel websites and airlines. Therefore, it tries to explain what the main reasons for attraction of this type of service. In this way, a model is proposed to evaluate how the constructs of perceived risk, complexity, relative advantage and communicability, mediated by attitude, influence the intention to purchase and the positive word-of-mouth. The model was tested using a structural equation, with data collected through an online questionnaire administered in order to evaluate each construct. The results confirm the confidence of the model and support the research hypotheses, with a good level of explanation of the dependent variables. The study presents consistent elements that can be considered by the companies that are in this segment to boost the use and the positive world of mouth of reservation sites, as well as points of attention that should be considered by the competitors of this type of service. Thus, a parsimonious model is presented, which consistently explains the purchase intention and the positive word-of-mouth of online booking sites.