Purpose: Renal size is an important indicator to determine adequate organ growth in children. The aim of this study was to estimate renal size with Technesium-99m dimercaptosuccinic acid (DMSA) scan and propose a simple formula for predicting renal length in normal Korean children. Methods: This study included 346 children (148 boys and 198 girls; age range, 1 month to 17 years) in whom renal length was measured using the DMSA scan. Patients with anatomical renal abnormalities or acute pyelonephritis were excluded. Children were divided into two groups: 214 children (61.8%) were less than a year old (group 1) and 132 (38.2%) were ${geq}1$ year (group 2). Results: Renal length was larger on the left side than the right side, and there was no significant gender-related difference in renal length. We propose the following formula for renal length based on the analysis of the 346 children in our study: the formula was as follows: $4.682{ imes}age(month)^{0.137}$, $R^2=0.780$. In group 1, the formula was renal length $(cm)=0.127{ imes}age(month)+5.144$, $R^2=0.354$, and in group 2, the formula was $0.334{ imes}age(year)+6.477$, $R^2=0.829$. Conclusion: It is difficult to establish simple formulae in infants ($R^2=0.354$). Therefore, further studies including relevant variables are needed for this age group. We proposed formulae to estimate renal length in Korean children over 1 year of age by using the DMSA scan.