Purpose: The purpose of this study was to compare the differences in characteristics, lactation problems, knowledge, and adaptation of breastfeeding between users and non-users of a lactation clinic. Methods: The descriptive study design was utilized using self-report questionnaires. 446 breastfeeding mothers participated in this study . Data were collected from lactation clinics, postpartum care centers, mother’s culture centers, public health centers, pediatrics and obstetrics & gynaecology outpatient clinics in Seoul, Gyeonggi province, and Chungcheongnam province from August 20 to September 30, 2011. The questionnaires to measure lactation problems, knowledge and adaptation of breastfeeding were used. Data were analyzed using SPSS ver. 18.0 for Windows. Results: There was statistically significant differences in the breast feeding problems(t=5.71, p<.001) and breastfeeding knowledge(t=2.87, p=.004) between users and non-users of a lactation clinic. Conclusion: The results of this study may provide a foundation to develop nursing intervention for mothers in breastfeeding, and an evidence to expand the role of nurses as breastfeeding specialists.