Background: Recognising that it is good practice, researchers are increasingly expected to involve stakeholders (i.e. patients, the public, health professionals and others) in systematic reviews, but there is currently a lack of evidence about how to do this.

Objectives: We aimed to synthesise evidence relating to stakeholder involvement in systematic reviews, and identify and describe methods of involvement.

Methods: A mixed-method synthesis of evidence, comprising (1) a scoping review to create a broad map of evidence; and, (2) a synthesis focused on evidence where methods of involvement were described. We comprehensively searched electronic databases (from 2010), completed pre-defined hand searching, and contacted experts. Two reviewers applied inclusion criteria. Papers from the scoping review judged to provide an adequate description of methods were included in the focused synthesis. Details of methods of involvement were extracted using pre-defined headings, presented in tables and described narratively.

Results: 12908 titles screened; 662 full papers considered, of which 294 met inclusion criteria for scoping review. 126/294 papers included in focused synthesis; 38/126 provided a good description of methods of involvement. Levels of involvement of stakeholders ranged along a continuum from minimal involvement to control (e.g. consumer authors). Involvement could be classified as either 'continuous' (throughout the review process) or 'one-time' involvement. Stakeholders could be described as having a managerial, oversight or responsive role. Examples of involvement were identified at all stages of the review process. Formal consensus decision-making techniques (Delphi approach, nominal group technique, ranking, voting) were used in almost half of identified examples.

Conclusions: There are a wide range of different methods for involving stakeholders in systematic reviews, and many are adequately described in current literature. Cochrane Learning have created learning resources based on this evidence which will support review authors in selecting and implementing methods of stakeholder involvement in future reviews.