Background: The effectiveness of mobile health (mHealth) is a controversial issue. For its wide-scale adoption and successful integration to the healthcare system, theoretical, methodological, and practical issues of mHealth should be well understood.

Objectives: The purpose of the study was to review the essential characteristics of mHealth and discuss what mHealth presents to research and theory.

Method: This review synthesized the studies focused on the adoption, design, and implementation of mHealth. The search strategy included reviewing electronic databases, key journals, web-based research and knowledge centers, and manual searching reference lists of the main studies.

Results: mHealth's core characteristics were specified as accessibility, inclusivity, patient's autonomy, customizability, increasing the accuracy of diagnostics and treatment, improvement in service quality, and testability. Opportunities and challenges in regards to theory and research were discussed.

Conclusions and implications: Using an integrated approach, this study identified and summarized the key issues to understand mHealth. Implications and recommendations for research and practice were provided.