PURPOSE: This study examined what characteristics and variables predict participation in support groups for women with breast cancer. METHOD: 282 women with breast cancer from 4 hospitals located in Busan were included in the study. Data was measured on each participant from September 2006 to February 2007. Data was collected using structured researcheradministered sheets and analyzed by descriptive statistics, t-test, chi-square test and logistic regression analysis. RESULTS: The clients reported medium levels of illness perception, anxiety and depression, stress with coping, social support and self-efficacy. 48.9% of women with breast cancer participated in support groups. Significant influencing factors on the participation in support groups were 'operation time(+)', 'illness perception(+)', 'social support(-)', and 'self-efficacy(+)' Those variables explained 73.4%. CONCLUSION: It is necessary to develop a strategy or promoting program for promotion of illness perception and self-efficacy of women with breast cancer. Thus, it is essential to provide participation to a support group to a women with breast cancer.