Aim: The main goal of the research is to determine whether the patients treated at the Clinic for Oncology and Radiotherapy of KBC Split use alternative and complementary methods of treatment. Other objectives are to determine the most commonly used methods, reasons for use, whether the patients discuss use the with doctors and nurses, patients' experiences of benefits and side effects of use, and reactions of healthcare staff to statements about use. Methods: The research was conducted at the Clinic for Oncology and Radiotherapy of KBC Split, using a survey questionnaire, on 200 respondents, the main inclusion criterion was that they were adults, oncology patients undergoing active oncology treatment. Results: The research confirmed the main hypothesis that patients at the Oncology and Radiotherapy Clinic of KBC Split use alternative and complementary treatment methods in 36% of cases. If we also take into account the fact that out of 128 participans, as many as 70 of them (54.6%) mention taking one of the offered preparations/methods, we can conclude that the third hypothesis is also confirmed. In addition to oncological treatment methods, the majority of participants use prayer (65.7%), vitamins and minerals (62.9%) and herbal preparations (55.7%) as complementary and alternative methods. The results of this study also confirmed the second hypothesis, which is that patients decide to use alternative and complementary methods immediately after the diagnosis of a malignant disease in 44.4% of cases. When asked about the reasons for using alternative treatment methods, the most common reason is the expectation of increased immunity (75%) and reduction of side effects. The fourth hypothesis of this study was confirmed in 50% of the cases where the respondents declare that they do not confide in their oncologist and in 87.1% of the cases in which they do not confide in the nurse about the use of CAM. The most common reason why they did not confide in an oncologist/nurse is that they were not even asked to do so (85.7%). The reactions of the oncologist/nurse to the respondents' statements about the use of alternative treatment methods are in 49.3% of cases such that they left the decision on further use to the patient, while in 46.7% of cases they provided them with support and understanding. Conclusion: Patients who are treated at the Clinic for Oncology and Radiotherapy of KBC Split use alternative and complementary methods of treatment, which they decide on most often immediately after diagnosis. Most often they use herbal preparations and vitamins and minerals and prayer. Patients do not discuss the use of alternative treatment methods with health staff at the Clinic in 50% of cases, most often because they are not even asked. The main reason for using KAM is the expectation that their immunity will increase.