BACKGROUND: In this study, we aimed to validate the agreement between pulmonary function measurements obtained with a portable spirometer and measurements obtained with conventional spirometry in Chinese pediatric and adult populations. METHODS: Pulmonary function testing was performed to evaluate subjects enrolled at Shanghai Zhongshan Hospital (n 5 104) and Shanghai Children's Medical Center (n 5 103). The portable spirometers and conventional devices were applied to each subject with a 20-min quiescent period between each measurement. Pulmonary function parameters of FVC, FEV 1 , peak expiratory flow, maximum expiratory flow at 25%, 50%, and 75% of FVC (MEF 25 , MEF 50 , and MEF 75 , respectively), and FEV 1 /FVC% were compared with intraclass correlation and Bland-Altman methods. RESULTS: A satisfactory concordance of pulmonary function was observed between spirometry measurements obtained with portable versus conventional spirometers. Intraclass correlation indicated excellent reliability (>0.75) for all pulmonary function indicators in pediatric and adult subjects. Significant positive correlations of all variables measured with different spirometers were observed (all P < .001). No significant bias was observed in either group, although limits of agreement varied. Funnel effects were observed for peak expiratory flow in pediatric subjects and for FVC, FEV 1 , MEF 50 , and MEF 25 in adult subjects. CONCLUSIONS: The portable spirometer is an alternative to the conventional device for the measurement of pulmonary function.