['Decision aids help patients make informed treatment decisions. Values clarification (VC) techniques are part of decision aids that help patients assimilate the information with their personal values. There is little evidence that these techniques contribute to enhanced decision making over and above the provision of good quality information.', 'To assess whether VC techniques are active ingredients in enhancing informed decision making and explain how and why they work.', 'Participants were randomly assigned to one of three groups: (i) information only, (ii) information plus implicit task, (iii) information plus explicit task. Thirty healthy women from a UK University participated by making a hypothetical choice between taking part in a clinical trial and having the standard treatment for breast cancer. Verbal protocols were elicited by think-aloud method and content analysed to assess informed decision making; a questionnaire was completed after the decision assessing decision preference, perceptions of decisional conflict and ambivalence. Data were analysed using multivariate statistics.', 'No participants changed their decision preference as a result of the VC techniques. Women in the explicit VC group evaluated more information in accord with personal values, expressed lower ambivalence, decisional uncertainty and greater clarity of personal values than those in the implicit VC and control groups. Feelings of ambivalence about both options were related to decisional conflict.'] Do why values elicitation techniques enable people to make informed decisions about cancer trial participation?