Objective: To understand: if professionals, citizens and patients can locate UK healthcare professionals' statements of declarations of interests, and what citizens understand by these., Design: The study sample included two groups of participants in three phases. First, healthcare professionals working in the public domain (health professional participants, HPP) were invited to participate. Their conflicts and declarations of interest were searched for in publicly available data, which the HPP checked and confirmed as the 'gold standard'. In the second phase, laypeople, other healthcare professionals and healthcare students were invited to complete three online tasks. The first task was a questionnaire about their own demographics. The second task was questions about doctors' conflicts of interest in clinical vignette scenarios. The third task was a request for each participant to locate and describe the declarations of interest of one of the named healthcare professionals identified in the first phase, randomly assigned. At the end of this task, all lay participants were asked to indicate willingness to be interviewed at a later date. In the third phase, each lay respondent who was willing to be contacted was invited to a qualitative interview to obtain their views on the conflicts and declaration of interest they found and their meaning., Setting: Online, based in the UK., Participants: 13 public-facing health professionals, 379 participants (healthcare professionals, students and laypeople), 21 lay interviewees., Outcome Measures: (1) Participants' level of trust in professionals with variable conflicts of interest, as expressed in vignettes, (2) participants' ability to locate the declarations of interest of a given well-known healthcare professional and (3) laypeoples' understanding of healthcare professionals declarations and conflicts of interest., Results: In the first phase, 13 health professionals (HPP) participated and agreed on a 'gold standard' of their declarations. In the second phase, 379 citizens, patients, other healthcare professionals and students participated. Not all completed all aspects of the research. 85% of participants thought that knowing about professional declarations was definitely or probably important, but 76.8% were not confident they had found all relevant information after searching. As conflicts of interest increased in the vignettes, participants trusted doctors less. Least trust was associated with doctors who had not disclosed their conflicts of interest. 297 participants agreed to search for the HPP 'gold standard' declaration of interest, and 169 reported some data. Of those reporting any findings, 61 (36%) located a relevant link to some information deemed fit for purpose, and 5 (3%) participants found all the information contained in the 'gold standard'. In the third phase, qualitative interviews with 21 participants highlighted the importance of transparency but raised serious concerns about how useful declarations were in their current format, and whether they could improve patient care. Unintended consequences, such as the burden for patients and professionals to use declarations were identified, with participants additionally expressing concerns about professional bias and a lack of insight over conflicts. Suggestions for improvements included better regulation and organisation, but also second opinions and independent advice where conflicts of interest were suspected., Conclusion: Declarations of interest are important and conflicts of interest concern patients and professionals, particularly in regard to trust in decision-making. If declarations, as currently made, are intended to improve transparency, they do not achieve this, due to difficulties in locating and interpreting them. Unintended consequences may arise if transparency alone is assumed to provide management of conflicts. Increased trust resulting from transparency may be misplaced, given the evidence on the hazards associated with conflicts of interest. Clarity about the purposes of transparency is required. Future policies may be more successful if focused on reducing the potential for negative impacts of conflicts of interest, rather than relying on individuals to locate declarations and interpret them., Trial Registration Number: The protocol was pre-registered at https://osf.io/e7gtq., Competing Interests: Competing interests: MMC has been paid for writing/broadcasting in relation to issues connected with campaigning around conflicts of interest. All authors have completed the Unified Competing Interest form (available on request from the corresponding author) and have no other declarations to make regarding support from any organisation for the submitted work; financial relationships with any organisations that might have an interest in the submitted work in the previous 3 years., (© Author(s) (or their employer(s)) 2023. Re-use permitted under CC BY. Published by BMJ.)