The use of unproven therapies is of concern for a number of reasons, including the lack of scientific evidence of support them, their potential financial costs and the possibility of interference with conventional treatment. This study explored the prevalence, predictors and experiences of unproven therapy use by cancer patients attending an oncology clinic at an Australian teaching hospital. A questionnaire was administered to patients whilst they were waiting for a consultation with their oncologist. A total of 173 patients were invited to participate, and 156 consented to complete the survey (90%). Over half the patients (81, 52%) had used at least one unproven therapy since their diagnosis, and 28% had used three or more. Patients most commonly practised mediation/relaxation, changed their diet and used multi-vitamins. Most expected that the therapies would aid their conventional treatments and make them feel more in control of their situation. Benefits reported were largely psychological, such as an increased sense of control or a reduction in anxiety. Younger patients, those with early stage or advanced metastatic disease and those who had used unproven therapies prior to developing cancer were more likely to use unproven therapies. Health professionals involved in the care of cancer patients should be prepared to discuss the use of unproven therapies and try to identify and deal with unmet needs to help patients to cope with their illness.