Background: Using evidence-based smoking cessation support tools double the chances of quitting, but uptake is low. An online decision aid could help smokers choose a fitting tool. We aim to reach expert agreement on the required content and attributes of such a decision aid (DA). Methods: A three-rounded Delphi study has partially been conducted. Seventeen smoking (cessation) experts filled out an open-ended questionnaire relating to a DA for smokers. In the second and third round the answers will be sent to a larger group to 1) rate these in terms of importance and 2) rescore their previous answers. Data will be analysed via descriptive techniques, e.g. interquartile deviations to measure consensus. Findings: Preliminary results of the first round show that there was little variation in terms of emerging main topic, i.e. all experts named important characteristics of smoking cessation support tools, decision aid functions and attributes, layout considerations and also how to use the DA in the current clinical context. However, only experts that were also health care professionals named important characteristics of the smoker. Discussion: The study will result in knowledge on expert agreement regarding a DA for smokers. Results from this study will inform development of said DA.