El Amrousy D, et al. - In this observational case-control study, researchers assessed the pulmonary function test (PFT) abnormalities, if any, in children with newly diagnosed chronic hepatitis B (CHB) infection over 3 years. One hundred newly diagnosed CHB children and adolescents were enrolled as the patient group that was further subdivided into two groups (50 patients each): inactive carriers (group I) and patients in immunotolerant phase (group II). The analysis was performed by only 90 patients. Fifty healthy children of matched age, gender and height served as a control group, the study was completed by only 45 of them. The data presented in this work showed a significant progressive reduction in forced expiratory volume in 1 s (FEV₁), forced vital capacity (FVC), forced expiratory flow, total lung capacity and diffusing capacity of the lung for carbon monoxide in CHB patient groups vs their pulmonary functions at the beginning of the study and with the control group, while FEV1/FVC and residual volume showed no significant change. Subclinical PFT anomalies occur more than the authors expected in children with CHB. PFT monitoring of pediatric patients with CHB is therefore recommended.