AIM: The use of complementary and alternative therapies (CAT) in oncology patients is increasing in incidence, with calls to routinely screen for their use. We introduced a screening tool as part of clinical care to identify CAT use. METHODS: We evaluated all patients who attended the radiation oncology outpatient clinic between December 2011 and July 2012, who had filled out the CAT screening tool, and evaluated types of CAT use, reasons for use and predictors of CAT usage. RESULTS: A total of 639 patients completed the CAT screening tool, which was 75% of eligible patients. There were 464 (72.6%) men and 175 (27.4%) women, with a mean age of 69.9 years (range 27-94 years). Prostate cancer was the predominant diagnosis (53.1%), followed by breast cancer (17.5%) and skin cancer (14.7%). Of these, 530 patients (82.9%) had used at least one therapy. Of the 530 patients using CAT, the most quoted reasons for use were to improve quality of life (42.6%), to boost the immune system and general health (33.6%), to increase energy levels (32.6%) and to live longer (28.9%). Of the 530 users, only 112 patients (21.1%) took CAT to help cure their cancer. Women were significantly more likely to use CAT, as were patients with breast cancer. CONCLUSIONS: The use of CAT in patients with cancer is prevalent and more frequent in our population than in other published studies. Few patients use CAT to improve their cancer cure, but rather use CAT for other reasons.