The findings of this study are published in: Purić, D., Petrović, M. B., Živanović, M., Lukić, P., Zupan, Z., Branković, M., Ninković, M., Lazarević, L. B., Stanković, S., & Žeželj, I. (2023). Development of a novel instrument for assessing intentional non-adherence to official medical recommendations (iNAR-12): A sequential mixed-methods study in Serbia. *BMJ Open, 13*(6), e069978. https://doi.org/10.1136/bmjopen-2022-069978. Please cite accordingly. This study aims to create valid and reliable short instruments to assess: - The frequency of Non-Adherence to official medical Recommendations (NAR practices) and - The familiarity and frequency of use of Traditional, Complementary and Alternative Medicine (TCAM practices). The developed extensive initial list of practices will be examined in terms of their internal structure and relation to other relevant variables so as to select a smaller number of items which will show optimal psychometric properties, to be used in future studies (within the project and beyond). Due to copyright issues, the Adherence Barriers Questionnaire (ABQ) was not used in the study. The items in Serbian are not an official Serbian translation. The ABQ is a copyrighted instrument and all requests should be sent to IPAM e. V., Wismar, Germany (abq@ipam-wismar.de).