The use of complementary and alternative medicine is spread wide over the world. The products of complementary and alternative medicine are used by healthy and sick persons. However, the purpuose of those products are different. The aim of this research was to get informations about the use of complementary and alternative medicine by the patients with an oncology disease who are treated in the Clinical hospital center Zagreb, Clinic of oncology. Hundred forty-four questionnaires was shared, and the response was 92 %. The bigest number of the respondents is suffering from malignant diseases of the digestive tract (47,7 %), and the malignant diseases of the urogenital system (19 %). Even 75,4 % of the respondents is treated with intravenous chemotherapy. A total of 45 respondents (35 %) is using methods of complementary and alternative medicine in his treatment. The most common method of treating is treating with medicinally herbs. As a reason why they use complementary and alternative medicine, the responders mostly believe that it will help them. More then a half of the responders (57,8%) informed they oncologist about the use of complementary and alternative medicine treatments. The reason of informing and not informing they oncologist about the use of complementary and alternative methods of treatment are similar to each other, which implies the need for overall education of the medical staff, as well as the oncology patients, about the good and bad effects of complementary and alternative medicine.