<i>Background:</i> Intra-abdominal fat (IAF) is a valuable predictor of cardiovascular morbidity. However, neither reference values nor determinants are known in children. <i>Methods:</i> IAF was assessed as sonographically measured intra-abdominal depth in 1,046 children [median age 7.6 years, interquartile range (IQR) 7.2–7.9; 54% boys] of the URMEL-ICE study. <i>Results:</i> The intraclass correlation coefficient for intraobserver agreement was 0.93. The median IAF showed a significant gender difference (boys: 54.6 mm, IQR 50.1–59.3, vs. girls: 51.7 mm, IQR 46.3–56.4; p < 0.001). Age- and gender-specific centiles were generated. IAF showed a positive correlation to systolic blood pressure [regression coefficient (β) = 0.24 mm Hg/mm; p < 0.001] and a negative correlation to HDL cholesterol (β = –0.01 mmol/l/mm; p < 0.001). IAF showed a positive association with increased paternal and maternal BMI (β = 0.28 mm/kg/m² and 0.27 mm/kg/m²; p < 0.001), increased weight gain in the first 2 years of life (β = 3.04 mm; p < 0.001), and maternal smoking during pregnancy (β = 2.4 mm; p = 0.001). Increased parental education was negatively associated with IAF (maternal: β = –0.65 mm/degree; p = 0.004, and paternal: β = –0.61 mm/degree; p = 0.002). <i>Conclusion:</i> Sonography was a reliable tool to estimate IAF. Factors influencing IAF included rapid infant weight gain, smoking during pregnancy, and parental BMI and education. Since IAF showed an association with cardiovascular risk factors even in prepubertal children, it might become a valuable predictor of cardiovascular vulnerability.