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Children are the biggest national investment that a society can make. With increased child population so too have their problems increased, amongst which are the increased incidence of street children, which as a result has endangered their health. This research is a descriptive and cross sectional study towards determining the effective factors on the self-concept of street children aged 6-12 years who were referred to the Khajouye Kermani culture house of Tehran in 1380. In this regard, 140 street children between the ages of 6-12 were chosen. The method was a 4-part questionnaire which included personal, family and societal information and questions related to the self- concept of the children. The data was collected by interviews with the children. In accordance with the average and the deviation criteria achieved, the level of self-concept was divided into four groups, extremely negative, negative, positive and extremely positive. The results showed that half of the subjects (50%) had very negative concepts of themselves and only 2.2% of them had a very positive self- concept levels. Therefore the street children had a very low self- concept level. Also as concerns the factors affecting self- concept was also a meaningful relationship between self- concept and some factors such as gender, education, level of income, duration of work, level of happiness within the family, counseling, reaction to the child's mistakes, having necessities for the home, adequate nutrition and clothing, having street friends before work (P<0.05). Therefore street children are at risk as regards their mental and physical development because they suffer from low self- concept levels and require special attention. Because of the vast responsibilities nurses can play an important role to improve of the health of these children.