This study investigated associations between complementary medicine use and treatment and illness beliefs. Previously validated questionnaire measures of treatment beliefs, illness beliefs, and complementary medicine use were presented and advertised online. Completed questionnaires were received from 247 participants. Logistic regression analysis showed that demographic characteristics, treatment beliefs, and illness beliefs accounted for approximately 36% of the variance in complementary medicine use. Separate analyses were conducted to predict use of different types of complementary medicine. The strength of associations between beliefs and complementary medicine use was related to the type of complementary medicine used. The results suggest that people use complementary medicine because they are attracted to it rather than because they are disillusioned with orthodox medicine, and that both treatment and illness beliefs have an important role in explaining why people use complementary medicine.