Vasilescu and colleagues are the first to provide confirmation that an imaging biomarker, parametric response mapping (PRM), has the ability to differentiate small airway disease (PRMSAD) from emphysema (PRMEmph) in patients with established chronic obstructive pulmonary disease (COPD)(1). This is of utmost importance given the urgent clinical and scientific need to noninvasively detect terminal bronchial pathology. COPD is characterized by the presence of persistent airflow limitation and respiratory symptoms. Airways smaller than 2 mm in internal diameter are the dominant site of airflow obstruction in patients with COPD. This obstruction is caused by a mixture of pathogenic events (with) in and around the small airways, namely, loss of airways (2, 3), thickening of remaining airway walls (3), luminal obstruction by endobronchial mucus, and loss of bronchiolar–alveolar attachments leading to reduced radial traction. Emphysema is a key pathological condition in COPD that is defined by an abnormal, permanent enlargement of airspaces distal to the terminal bronchiole, accompanied by destruction of their walls and without obvious fibrosis. Whereas in an editorial addressing the landmark study of McDonough and colleagues (2), Mitzner (4) questioned whether emphysema formation starts in the small airways or lung parenchyma, accumulating evidence now strongly suggests that small airway disease precedes emphysema formation (2, 3, 5). It has been demonstrated that a significant proportion of terminal and transitional bronchioles are lost in lung samples from patients with COPD without signs of emphysema (2, 3), and that the