Background: Many studies in health sciences research rely on collecting participantreported outcomes and attention is increasingly being paid to the mode of data collection. Consideration needs to be given to the validity of response via different modes and the impact that choice of mode might have on study conclusions. Objectives: (1) To provide an overview of the theoretical models of survey response andhow they relate to health research; (2) to review all studies comparing two modes ofadministration for subjective outcomes and assess the impact of mode of administrationon response quality; (3) to explore the impact of findings for key identified health-related measures; and (4) to inform the analysis of multimode studies. Conclusions: Researchers need to be aware of the different mode features that could have an impact on their results when selecting a mode of data collection for subjectiveoutcomes. Further mode comparison studies, which manipulate mode features and directly assess impact over time, would be beneficial.