People's privacy concerns about electronic health records (EHRs) have been widely discussed. Given that in principle, patients have the right to control their information in EHRs, the system will not reach its full potential without their support. Although human beings are generally inclined toward privacy, contextual differences play a role in individual decisions to disclose personal information. Likewise, patients exhibit different responses in terms of sharing their health information in diverse scenarios. Empirical work on patients' attitudes towards the secondary use of their health information is scarce. This study aims to investigate individuals' willingness to share their health information based on anonymity, information type (partial vs. whole), and the type of information user (health professionals, health researchers, health-related governmental agencies, and other governmental agencies). Furthermore, this study attempts to examine the effects of interaction between the three factors. A survey was conducted in South Korea, and the data obtained were analyzed by ANOVA. Despite the recent rapid diffusion of EHRs in South Korea, there is little discussion of patients' privacy in society. The results show that, although anonymity and the user type have a significant effect on willingness to share health information, the information type has no significant effect. The results also indicate that the willingness to share was higher for health-related governmental agencies and health professionals than for other governmental agencies. The findings reveal that, although willingness to share anonymous information does not vary significantly, the willingness differs for identified information. The study contributes to research on patients' privacy behavior by analyzing their comprehensive responses to health information-sharing investigations.