The diagnosis and management of the most prevalent chronic respiratory diseases partially rely on parameters obtained from pulmonary functional tests (PFTs), including spirometry, plethysmography, and carbon monoxide diffusion capacity (DLCO) measurement. In practice, the interpretation of PFTs' parameters is based on international recommendations issued by renowned scientific societies such as the American Thoracic Society (ATS) and the European Respiratory Society (ERS). The interpretation standards for PFTs established by ATS/ERS in 2005 were updated in 2022. According to the ATS/ERS-2022 standards, the interpretation of PFTs can be summarized in five steps. The first step involves comparing the determined parameters with those observed in a reference population of healthy individuals. This step helps determine whether the determined parameters are low, normal, or elevated. The second step aims to identify potential ventilatory impairments, such as obstructive and/or restrictive ventilatory impairments, which can be observed in certain chronic respiratory or extrarespiratory diseases. The third step involves assessing the severity of the identified ventilatory impairment or the decrease in DLCO. The fourth step entails evaluating the response to bronchodilator testing, if performed. Finally, if previous PFTs results are available, it is important to identify significant changes in certain PFTs parameters over time by comparing current and previous results. This clinical practice guide provides a comprehensive synthesis of the different steps in PFTs interpretation, taking into account the recommendations from ATS/ERS-2022.