Motivated by the fact that social media are continuously gaining in popularity, firms are piloting different approaches of promoting their products and services. However, there is much debate in the academic and business community about the effectiveness of social media as a platform for marketing. Specifically, practitioners are concerned with how Word-of-Mouth (WOM) is spread through these sites, and what aspects facilitate users in doing so. The aim of this research is to elucidate the motivations for WOM over social media based on utilitarian and hedonic theories. Partial Least Squares (PLS) analysis is performed on data obtained from 169 social media users to test our research model. Outcomes indicate that both, utilitarian and hedonic motivations impact WOM. Utilitarian motives are triggered through customized advertisements, while hedonic motives through the ability to socialize during product browsing.