HTA can be defined as ‘a multidisciplinary process that uses explicit methods to determine the value of a health technology at different points in its lifecycle. The purpose is to inform decision-making in order to promote an equitable, efficient, and high-quality health system.’ (O’Rourke et al. 2020.) HTA is deployed in more than 30 countries, using robust scientific evidence and deliberation to guide policy decisions about medicines, devices, interventions, procedures, and other health technologies. HTA often seeks to determine the value of a new health technology based on clinical and cost effectiveness evidence. However, when HTA was first described by the US Office of Technology Assessment in 1976 it was envisioned as a means of considering all the implications of introducing a new health technology. As such, wider societal aspects – including the impact for patients and their families, legal and ethical issues, and the environment – were considered essential to any assessment of the consequences of the way a health technology was or was not used. In some HTAs, this wider consideration of consequences continues to inform the determination of value and has important implications for the evidence considered and deliberative frameworks used. One of the accompanying footnotes to O’Rourke at al.’s definition of HTA, Note 3, recognises that value has many dimensions and the overall value of a health technology ‘may vary depending on the perspective taken, the stakeholders involved, and the decision context’ (2020). As such, it appears to support a view that the evidence base for HTA is robust but not neutral. Determining value depends on your perspective, which shapes the questions you ask in an HTA, the evidence you consider, and how you interpret it. This understanding of value determination has implications for the goals of patient involvement and subsequent use of research into patient aspects (known as patient-based evidence) and approach to patient participation. For example, patient-based evidence and participation may be used in recognition that traditional scientific evidence (such as randomised controlled trials) may not capture the outcomes that are most important to patients. It needs to be interpreted in the light of patients’ needs, preferences, expectations and experiences, especially for application in the local healthcare context. As such, it often provides an important opportunity for those with lived experience of a condition to challenge assumptions made about patients and to direct inquiry to more relevant issues. Thus, patient involvement in HTA can be viewed as a means to patient-centred healthcare policy, ‘ensuring fair and transparent allocation of resources informed by the needs, preferences and experiences of patients’ (Facey et al. 2018). There are many parallels between clinical guideline development and HTA in terms of scientific rigour and fair processes to translate international evidence into improvements in healthcare at a national or regional level. However, there is a difference in the way the evidence flows into decision making. Although clinical guidelines inform improvement in the whole care pathway and are focused on informing clinicians of best practice (provider decision making), HTA focuses more on decisions about a specific item in the care pathway and may be linked directly to reimbursement (payer decision making). HTA is often described in 3 steps: Assessment: critical review of published or submitted evidence about the clinical effectiveness or cost effectiveness of a health intervention.Appraisal: wider consideration of the evidence in the local context with value judgements about value and appropriate use.Decision making: decisions about whether health interventions are made available, and to whom, in a health system – access or reimbursement decisions. (Garrido et al. 2008.) Bodies that undertake HTA vary widely and may be responsible for assessment, appraisal or both, but all seek to inform decision making in some way. Furthermore, many of the HTA bodies are part of larger organisations that undertake a range of evidence-based work in the health system and this often includes clinical guideline development. Hence sharing approaches, while recognising differences, seems appropriate. As HTA has become increasingly associated with treatment reimbursement and access issues, it has become more contentious. In some countries this has resulted in strong patient advocacy challenges and political drives to involve patients in the processes. Some HTA bodies have responded by creating transparent processes for patient participation in the HTA process and developing approaches for obtaining patients’ needs, preferences, expectations and experiences (Facey et al. 2010). However, this involvement is not widespread or consistent. Some HTA bodies are reticent about involving patients or including their perspectives, especially when a health technology’s value is seen as scientifically determined and patient involvement considered a source of bias rather than evidence and perspective. If such concerns are not satisfactorily explored and resolved within an HTA body (and its stakeholders), patient involvement is unlikely, or may at best be tokenistic because of its perceived threat to the credibility and legitimacy of HTA rather than improving the robustness of HTA. Without careful consideration of an HTA body’s beliefs and norms before committing to shared goals for patient involvement, HTA bodies risk setting up unrealistic expectations for patient communities. As a result, patient input and patient-based evidence will be perceived to have little or no consequence because of implicit or explicit barriers. Hence guidance was needed to provide practical ways in which patients could contribute to HTA and decision making with credibility and legitimacy (Boivin et al. 2014). Clarification was also needed about the complementary but different roles for evidence generated from research into patients’ needs, preferences and experiences using robust, scientific methodology and insights gained from patient participation in HTA processes. Such participation includes patient input from written submissions and committee membership.