The number of social networking site users is rapidly growing. Users are encouraged to disclose their data on these sites. By disclosing their data, users expose themselves to a number of risks. Studies show that users are concerned that their data will be used in unforeseen ways and would like to be informed about how their data is used. Yet, even though users express high levels of privacy concerns they are at the same time being relatively uneducated in disclosing their data. Therefore, it is important to urge users to become more aware of the privacy protocols of social networking sites. Studies have shown that in turn, social networking sites can expect more trust from their users if they provide high quality information and educate them. Therefore, it’s important to understand what role informed data disclosure has in trusting social networking sites. With an aim to research this topic, theoretical part of the thesis focuses on a literature review of the relevant contributions to the topics of data disclosure on social networking sites, privacy awareness and trust in social networking sites. The empirical part of the thesis contains qualitative research in the form of six semi-structured interviews. The research showed that even when users are aware of the possible risks, they consciously expose themselves to possible risks when disclosing their data on social networking sites and mostly do not change their behaviour. Trust in social networking sites has been shown to decrease as the privacy awareness of users increases.