Objectives The study was designed to find out the relationships between low weight and growth, skeletal maturity among children by analyzing body composition and bone age. Methods Subjects were composed of 336 children from six years to seventeen years of age, without any other diseases related to growth, who visited the department of oriental pediatrics East West Neo Medical Center at Kyung Hee University and were measured their body composition and bone age. Results There were significant correlations between decreasing of RH-MPH(%) and low weight. 1. As obesity index decreased, the RH-MPH was also decreased. 2. The RH-MPH(%) of the low weight group according to the obesity index classification was significantly decreased than that of the normal weight group. 3. The skeletal maturity was more decreased in the low weight group. However, the differences between the two group was not significant. 4. The RH-MPH(%) was increased in children who developed secondary sexual character. Skeletal maturity was decreased in children who developed secondary sexual character. 5. The RH-MPH(%), and skeletal maturity was not significantly different between males and females. 6. Only in the case of children without development of secondary sexual character, low weight caused significant RH-MPH(%) decrease. Conclusions Low weight children might be smaller than what it supposed to be. Also, low weight could affect body development more to the children than to the teenager.