An update for the standardization of spirometry was published in 2019, to take full advantage of current technical capabilities, which includes enhanced quality assurance approaches. Aims: Determine the impact of the different quality control (QC) criteria between the 2005 and the 2019 ATS/ERS guidelines and describe the success rate in spirometry execution in a paediatric lung function lab; report compliance with QC criteria and identify the least fulfilled criteria. Methods: For each spirometry: start of test criteria (SOT), end of test criteria (EOT), number of acceptable, reproducible manoeuvres according to 2005 and 2019 guidelines were considered. Spirometry?s QC fulfilled criteria were quantified and compared (?2test, McNemara test; SPSS®2021). Results: 404 spirometries were analysed of which 237 (59%) were from male children, median age 12 (4-18) years old. Acceptability and repeatability were met in 300 (74%) by 2005 and 335 (83%) by 2019 guidelines, which was significantly different (p<0.01). For both analyses, SOT was met by more than 90% and extrapolation volume was achieved in almost 80% of exams. EOT was the least met criteria. 104 (26%) spirometries did not reach QC according to 2005 guidelines, compared to 69 (17%) as per 2019 guidelines. With the introduction of usability criteria, 17 (25%) were classified as uninterpretable and 52 (75%) met some QC criteria. Conclusion: More than two thirds of all children attained QC criteria. Performing good quality spirometry in pediatrics is possible. The new 2019 guidelines overcome difficulties encountered over the years in children. The objective quantification of quality and the reformulation of acceptability and repeatability is a clear step forward.