Renal parenchymal thickness was measured at different regions and levels through the kidney in 162 abdominal computed tomography (CT) examinations of children 5 months to 14 years old. The transverse diameter of the first lumbar vertebra (L1) was also measured, in order to take into account the child's body habitus. All patients were examined with an indication other than renal disease and had no abnormal CT findings in the retroperitoneum. Renal parenchyma increased in parallel with the transverse diameter of L1 and did not depend on age or sex in children of the same body format. There were no significant differences in size between the right and the left kidneys. Renal measurements were tabulated on reference tables, as an aid in the assessment of renal parenchymal thickness in children undergoing abdominal CT examination.