This systematic review describes characteristics of portal users and their perceptions of this emerging technology. Recent empirical evidence (2010-2016) was reviewed to answer three questions: (1) What are the characteristics of electronic patient portal users? (2) What are patient-perceived facilitators of electronic patient portal use? (3) What are patient-perceived barriers to electronic patient portal use? Characteristics of portal users are described according to three broad categories: demographic characteristics, patterns of use, and complexity and duration of disease. Three themes were found related to patient-perceived facilitators of use: provider encouragement, access/control over health information, and enhanced communication; two themes were found related to patient-perceived barriers to use: lack of awareness/training and privacy and security concerns. Understanding a patient’s perception of technology is paramount in optimizing use. These insights will allow for development of better products and clinical processes that facilitate broad goals of improved use of information technology. Policy and practice implications are discussed, as well as suggestions for future research.