Brands have been changing the way the connect and relate with their customers. Communication through social networks and the reference individuals and groups has been increasing. Still being one of the most important social networks, facebook, keeps being a mean of promoting brands. This social network allows consumers to read other opinions about brands and products and share their own opinions. Therefore, using a convenience sample of 719 individuals, aimed to understand the influence of eWOM generated by reference groups on Facebook, in Portugal. It was concluded that, although Facebook is not a major source to search information on products, the larger the search information and online contribution (information sharing) on Facebook, the greater the trust in eWOM obtained on the same social network. Respondents who contribute most online are also those who seek for information online and rely more on that information. It was also found that the opinions expressed by reference groups on Facebook are positively correlated with confidence in eWOM and purchase decision. Finally, we concluded that the reference groups that have more influence on trust in eWOM and seeking information on Facebook are: users on the brands pages, users in discussion groups, friends and other users.