This study was conducted to investigate and compare the degree of professional self -concept (PSC) of the psychiatric mental health nurse practitioners (PMHNP) in hospitals and public health centers and to identify the factors predicting PSC of them, in order to provide basic data for developing PSC increasing program PSC. The 355 PMHNP were sampled from the university or general hospitals. mental hospitals, community mental health centers and public health centers across the country. The scales used in this study were PSCNI by Arthur (1990), PSI by Heppner & Petersen (1982) and the Index of work satisfaction by Slavitt et al. (1978). The results of the study were as follows : 1. The average item score of PSCNI of PMHNP in hospitals was $2.83pm0.27$, and that of PMHNP in public health centers was $2.76pm0.28$. There was significantly different between two groups (p=0.0202) 2. A comparison of the scores for the dimensions of the PSCNI were as follows ; the mean item score of professional practice of nurses in hospital was $2.90pm0.30$, and that in public health centers was $2.83pm0.35$. There were significant differences between two groups in the scores of professional practices (p=0.0315), leadership (p=0.0071) and skills (p=0.0231). 3. There were significant differences between two groups according to education (p=0.0057) with no significant interaction effect of group and education. 4. Job satisfaction (JS) was the highest factor predicting PSC of PMHNP in hospitals $(34.5\%)$, and problem solving inventory score (PS) was the highest factor predicting PSC of PMHNP in public health centers $(33.6\%)$. JS and PS accounted for $42.6\%$ in PSC of PMHNP in hospitals. and PS, JS, age, marital status, religion, and career accounted for $57.6\%$ in PSC of PMHNP in public health centers. In the light of these results. to gam the professional self-concept. nurses should be educated continuously through role modeling in clinical nursing and research. Also, nurse educators and administrators need to develop programs and policies to increase professional self-concept of nurses, particularly of community PMHNP.