Objective To investigate the accuracy of three-dimensional ultrasound volumetric measurements for children's bladder. Methods The bladder volumes of 238 children aged 9 months to 16 years (male:106;female:132) in Shenzhen Children's Hospital underwent real-time three-dimensional ultrasound for volume measurements. These cases were divided into six groups according to the body surface area:(0.36~0.60) m2 (27 cases), (0.61~0.78) m2 (66 cases), (0.79~0.89) m2 (52 cases), (0.90~1.05) m2 (33 cases), (1.06~1.20) m2 (30 cases) and (1.21~1.78) m2 (30 cases). The bladder volume measured by GE Voluson E8 and Philips iU22 were compared with the actual volumes of discharge urine. The relation between bladder volume measurements and the actual volume of discharge urine was analyzed. Results Children's bladder volume increasesd with the body surface area (F=33.53, P<0.05) and showed positive correlations with the body surface area (r=0.679, P <0.05). Compared with the actual volume of discharge urine, each group's bladder volume measurements obtained by three-dimensional ultrasound were lower and the results were as follows:[(47.80±30.33) ml vs (82.24±49.63) ml, (77.20±39.72) ml vs (139.98±79.03) ml, (95.96±50.79) ml vs (175.96±101.70) ml, (117.46±54.17) ml vs (206.62±86.22) ml, (145.53±73.60) ml vs (253.33±135.09) ml and (220.27±110.34) ml vs (327.42±165.45) ml]. The differences between children's bladder volume measurements and the actual volume of discharge urine were statistically significant (t=3.19, 5.53, 5.08, 4.49, 3.84 and 3.00, all P <0.05), but children's bladder volume showed positive correlations with the actual urine volume (r=0.881, P<0.05). The bladder volume measurements by spheroid formula based on two-dimensional ultrasound are lower than the actual volume of discharge urine, and the results were as follows:[(50.38±36.94) ml vs (82.24±49.63) ml, (86.77±62.34) ml vs (139.98±79.03) ml, (102.69±60.21) ml vs (175.96±101.70) ml, (107.94±55.14) ml vs (206.62±86.22) ml, (145.31±66.01) ml vs (253.33±135.09) ml and (222.77±132.59) ml vs (327.42±165.45) ml]. The differences were statistically significant (t=3.03, 4.01, 4.47, 4.95, 3.94 and 2.75, all P <0.05), but children's bladder volume showed positive correlations with actual urine volume (r=0.326, P <0.05). Conclusions Three-dimensional ultrasound volumetric measurements for children's bladder is feasible and in clinical application, the factors of children's growth should be take into account. Combing regression equation, children's bladder volume can be more accurately quantified.