An increasing number of persons with cancer decide to choose complementary and alternative medicine. The purpose of the paper was to check the status of the use of complementary and alternative medicine methods in oncological patients and to compare health behaviours of patients using Complementary and Alternative Medicine (CAM) with those using neither of these methods. The studies were conducted from August till January 2020 in the Oncology Center in the south-eastern Poland. A cross-sectional study was conducted in a group of 208 oncological patients. The authors' own questionnaire and the standardized Health Behaviour Inventory were used. Most of the patients (85,09%) declared that they used complementary and alternative medicine methods. The most common methods chosen by the respondents included vitamin C, green tea and prayer. The vast majority of the respondents did not inform their oncologist about the use of CAM. 45,19% of the respondents had a high rate of health behaviours. It was observed that there was no communication related to the use of CAM among the patients and healthcare staff. Patients using CAM demonstrated more positive health behaviours than those who were not using these methods.