Background and objective Global Lung Function Initiative (GLI) 2012 equations were developed to resolve the age-related disparity in interpreting spirometry results. Local validation of the equation is needed, especially in Northeast Asian children. This study evaluated the GLI equation in Korean children. Methods Spirometry indices (FEV1, FVC, FEV1/FVC and FEF25-75 and clinical information were gathered from three population-based birth cohorts. Predicted GLI reference values and z-scores of spirometry results were calculated for 1239 healthy children. The mean, standard deviation of z-scores were compared to the expected 0 and 1. Probabilities of falling below the lower limit of normal [LLN] (z-score: -1.64) were compared to the expected value 5scores were assessed according to low (2) BMI z-score groups. Results Mean z-scores significantly differed from 0 for FEV1/FVC in males (mean [95: 0.18 [0.08, 0.27]) and FEV1 and FVC in females (-0.23 [-0.31, -0.15] and -0.26 [-0.36, -0.16], respectively). The standard deviation was larger than 1 for all variables in males and FVC and FEV1/FVC in females. The probability of falling below the LLN was significantly larger than 5 (12.139.64, 14.77]), FVC (15.8613.06, 18.81]), and FEF25–757.315.29, 9.49]) in males and FVC (11.919.40, 14.60]) in females. FEV1 and FVC z-scores increased across low to high BMI groups, and FEV1/FVC decreased from low to high BMI groups. Conclusion GLI equations marginally differ from real-world values, which should be considered by pulmonologists in practice or research.