Complementary and alternative medicine (CAM) has gained in popularity among cancer patients in recent years. The use of CAM in cancer patients is common with about one third of patients using some form of CAM in Western countries. The purpose of this study was to analyze the use of CAM and determine what factors affect to use CAM among cancer patients to provide CAM therapy information and assist therapy selection among various CAM therapies to cancer patients. The design of the study was descriptive cross-sectional, and data were collected using a 16-item questionnaire. This study was conducted in subjects with confirmed diagnosis of stomach, colon, liver, or pancreas cancer, in both out-patients clinics and inpatients setting in a tertiary hospital in Seoul Korea. As a result, among the participants, past or current CAM use was reported by 75%, which shows a statistically significant difference in income groups(P<0.05), but no difference in age and religion groups. The most common therapies use by cancer patients included traditional Korean medicine (32.1%), folk remedies (26.6%), exercise (14%), dietary supplements (11.6%), physical therapy (9.9%), diet therapy (5%), and meditation (4%). 77.8% of patients show satisfaction and 64.4% shows perceived effectiveness of CAM. Male patients with higher income, and previous treatment were more likely to use CAM. The main benefits from CAM reported by cancer patients were psychological improvement and symptom improvement. Of the cancer patients used CAM, 30.9% were dissatisfied, 25.8% did not have benefits from the use, and 7.6% experience side effects. Cancer patients who prefer CAM (more than 3 kinds) used it to cure cancer, on the contrary, the one who do not prefer CAM used to improve symptoms and psychological stability. The main sources of information about CAM were family and friends(54.4%), and media(24.5%), doctor and nurse(18.3%), and religion group(2.6%). Findings suggest that due to the relatively high use of CAM among cancer patients in Korea, this topic should be taken into account in the development of a holistic approach to cancer patients and efficient cancer patients management system and proactive and consistent management of CAM is necessary in the health care system in Korea.