Use of complementary and alternative medicine (CAM) has been reported to be more and more frequent among cancer patients in USA. The aim of this study was to analyze among French cancer patients the prevalence of CAM use, focusing on antioxidants (AO) that could interfere with antitumor agents. Seventy-nine patients, treated by antitumor chemotherapy in oncology day care unit, participated to an interview (medium age ?= ?60 years old). CAM use was reported by 42% of patients: mostly AO (24%) (selenium, green tea and vitamins ACE, more specifically), but also relaxation, acupuncture, hypnosis (19%) and homeopathy (15%). Among patients using CAM, 66% of them indicated that their physicians were not aware of this use and 47% of them thought that CAM use was safe. Nevertheless, for seven patients who have taken AO, previous in vitro and preclinical studies suggested interactions with antitumor chemotherapy. Therefore, CAM use and, more specifically, AO use is common among cancer patients treated by antitumor chemotherapy in France. Nevertheless, AO could generate interactions with conventional treatment. Clinical studies are warranted to evaluate these interactions, and adequate communication with patients is needed.