E-professionalism, as a derived form of professionalism, ad it can be defined as implementation of the principles of “traditional” professionalism in online activities. Aim of this dissertation is to define e-professionalism, develop measuring instruments for the assessment of e-professionalism of doctors of medicine and dental medicine and to compare e-professionalism of doctors of medicine and dental medicine in the Republic of Croatia. The research was conducted using the survey method, the online survey technique on a non-probabilistic sample of doctors of medicine and dentists who use social networks. A total of 1,013 responses were collected, of which 753 use a social network. For the purposes of determining e-professional behavior, normative framework was created based on three relevant sources, and it is shown that e-professionalism can be conceptually divided into two aspects: the aspect of dangers of social networks, like losing privacy of doctors' profiles, contact with patients and the fair distribution of resources, and the aspect of the benefits of social networks that include proactive posting of medical information of public health interest and scientific objectivity. The result of the process of creating and validating measuring instruments are two validated indices that researchers in the fields of occupational sociology and medical sociology will be able to use in future research. The results of the incidence of unprofessional behavior on social networks show that the highest incidence of unprofessional behavior is lack of control of the visibility of posts on social networks, followed by the lack of seeking permission from associates before tagging them in posts. The lowest incidence of unprofessional conduct was in HIPAA violations (Health Insurance Portability and Accountability Act) such as publishing information and photographs of patients and including patient data collected through social networks in the medical records without the patient's knowledge. There is a very strict perception of the professionalism of posts on social networks, which results in doctors of medicine and dental medicine successfully recognizing behaviors that are serious violations of professionalism, but they also strictly judge behaviors that are not violations of professional norms. Results also showed some significant differences between two professions. Doctors of dental medicine are more active on social networks and access them more often than doctors of medicine. Also more doctors of dental medicine use social networks for professional purposes and are more likely to interact with patients through social media than doctors of medicine. Finally, the paper identifies predictors of two aspects of e-professionalism. Greater acceptance of attitude toward ethical use of social networks in interaction with patients is the strongest predictor of unprofessional behavior on social networks, followed by the frequency of access to social media profiles (those who access more often have a higher frequency of unprofessional behavior). In contrast, established predictors of benefits of social networks, such as the potential for proactive posting of professional information of public health interest, show that the most important predictors are age and attitude about social networks, with older doctors of medicine and with positive attitudes about social networks do this more often.