Bronchiolitis, encompassing a spectrum of airway pathologies with significant clinical impact and varying treatments, poses a challenge for radiologists due to the frequent overlap of imaging findings. These pathologies are categorized into cellular bronchiolitis, characterized by centrilobular nodules with or without a 'tree-in-bud' pattern, and fibrotic bronchiolitis, associated with mosaic attenuation pattern. Within cellular bronchiolitis, numerous entities exhibit distinct imaging findings and associated clinical data that aid in diagnosis. Fibrotic bronchiolitis represents a pattern often associated with a clear clinical background, such as lung transplantation or connective tissue diseases (table 1).

Table 1: Figure 26. Small airways diseases summary, including etiology, pathophysiology, main imaging findings, auxiliary findings, and relevant clinical information.