Purpose: The objective of this study was to identify the effectiveness of continued breast feeding and maternal identity between rooming-in and not rooming-in groups of mothers in post partum care. Method: The subjects were selected by convenient sampling, with 95 women in childbirth completing a questionnaire. The data were collected on the 2nd day after delivery by questionnaire, and after the 4th and 8th weeks by telephone interview. Measures used in this study included general characteristics, breast feeding related characteristics, and the maternal identity scale revised by Koh(1996). The data were analyzed with the SPSS program, and the Chi-test and t-test were used to identify the effect on breast feeding and maternal identity. Results: Continued breast feeding up to 4 weeks after deliverly was not statistically significant between rooming-in and not rooming-in group, but beyond 8 weeks of deliverly, it was significantly different in rooming-in group(p<.01). Maternal identity was significantly higher in rooming-in group than in not rooming-in group(<.01). Conclusion: Mothers preferred rooming-in system because it helped breast feeding and baby care. Rooming-in system provides self confidence in taking care of baby, knowledge about breast feeding and stimulates early phase lactation. We recommend rooming-in system in hospitals to promote breast feeding and maternal identity. Nurses are encouraged to discuss prenatal breast feeding before delivery and rooming-in care should be planned individually for continuation of breast feeding and formation of maternal identity.