BACKGROUND: Dietary supplements (DS) have been increasingly utilized as a way of the promoting health and complementary therapy. This study aimed to evaluate the patterns of dietary supplement use in Korean cancer patients and to examine the related factors. METHODS: Between April and May of 2008, 366 patients who were hospitalized for diagnosis and treatment of cancer in a university affiliated tertiary hospital were surveyed using a self-administered structured questionnaire after receiving written informed consent. Among them, 322 patients with adequate answers were fi nally included. RESULTS: Two hundred forty patients (72.3%) reported to have ever taken DS with the mean number of 3.6 +/- 2.98. Vitamins were the most frequently used, followed by ginseng steamed red, ginseng, and glucosamine. The most infl uential factor regarding DS use was the recommendation by family members or relatives. The main reason for DS use was for resolution of fatigue, followed by supplementation of therapy, and immune enhancement. Information concerning DS most eager to know about was the effect of DS (44.6%), followed by interaction of DS with therapeutics (33.2%). Doctor (74.4%) was the most preferred health care provider to be consulted concerning DS, but only 34% of DS users have actually consulted with a doctor. Multiple logistic regression analysis showed that increasing age, Catholicism, and higher educational level were associated with higher use of DS. CONCLUSION: DS use was very prevalent in cancer patients. In spite of the great need, only small proportion of cancer patients using DS has consulted with a doctor.