Background: Studies on Post-COVID-19 Condition in adults have shown a deterioration in pulmonary function tests (PFTs), mainly diffusion limitation. Among pediatric population data are scarce.

Aim: To characterize PFTs of children with respiratory complaints and post-COVID-19 condition.

Methods: A prospective study of children presenting to a designated clinic for Post-COVID-19 Condition from 11/2020 to 12/2022. Patients with respiratory complaints underwent structured interview, chest X-ray (CXR) and comprehensive PFTs.

Results: 185 children at a mean age of 12.4 years (SD 4.06) were included. Average time from confirmed infection to evaluation was 176.5 days (SD 105.5). The majority were previously healthy (137, 74%); history of asthma was reported in 10 (5.4%). CXR was normal in 122/183 (67.8%). Abnormal spirometry was demonstrated in 20/169 (11.8%), all with mild obstructive pattern as indicated by FEV1/FVC < 80% and/or positive exercise challenge test and/or reversibility post bronchodilators; of these, only 2 had asthma. Total Lung Capacity was normal in all tested individuals. Diffusion was reduced in one patient (1/134, 0.7%), after a severe acute illness. LCI was elevated (>7.5) in 41/113 (36.3%). FeNO was elevated in 30/141 (21%). 33 children had repeated PFTs > 30 days post the first test; All had normal PFTs upon re-testing, including 7 (21.2%) who had mild obstructive pattern PFTs at presentation.

Conclusion: In children with respiratory symptoms post COVID-19, PFTs showed a mild obstructive pattern in 12%, the majority without a history of asthma. Improvement in PFTs was witnessed in long-term follow-up. As opposed to reports in adult population, diffusion limitation was not present.