Abstract <p>A significant number of non-idiopathic pulmonary fibrosis (IPF) cases follow an ‘IPF-like’ trajectory, known as progressive pulmonary fibrosis (PPF). PPF is associated with increased mortality. One of the criteria for identifying PPF is progression of fibrosis despite conventional treatment on serial high-resolution computed tomography. Progression may be identified by an increased overall extent of fibrosis on CT. However, an increased severity with the same overall extent should also be identified as progression. Radiologists play a critical role in the management of patients with PPF, as the accurate identification of radiological progression may allow patients to commence antifibrotic drugs, which have been shown to significantly reduce subsequent decline in lung function.</p> Key Points <p><Emphasis Type="BoldItalic">Question</Emphasis> <i>Non-idiopathic pulmonary fibrosis (IPF) disease can follow an ‘IPF-like’ trajectory, known as progressive pulmonary fibrosis (PPF), which is associated with increased mortality.</i></p> <p><Emphasis Type="BoldItalic">Findings</Emphasis> <i>One criterion for PPF is radiological progression, characterised by an increased overall extent or an increaed severity with the same overall extent.</i></p> <p><Emphasis Type="BoldItalic">Clinical relevance</Emphasis> <i>Radiologists play a critical role in identifying PPF, which may allow patients to commence antifibrotic drugs.</i></p>