The prevalence of complementary and alternative medicine (CAM) use among oncology patients ranges from 30 to 80%, particularly higher in the United States compared to Europe. However, limited research exists on the attitudes of healthcare professionals and oncology patients toward CAM, especially within Western evidence-based medical settings. This study aims to address this gap by assessing CAM use prevalence among healthcare professionals and oncology patients and analyzing their cognitive, affective, and behavioral attitudes. Additionally, it explores the influence of sociodemographic factors and personal experiences on these attitudes. A cross-sectional survey was conducted between November 2022 and May 2023 at University Hospital Center Sisters of Mercy, Zagreb, Croatia. The study included 832 participants: 411 oncology patients and 421 healthcare professionals (100 physicians, 321 nurses/technicians). Data were collected using modified versions of the Health Belief Questionnaire (CHBQ) and Integrative Medicine Attitude Questionnaire (IMAQ). Statistical analysis included descriptive methods and tests such as Chi-square, Mann-Whitney U, Kruskal-Wallis, ANOVA, and