Respiratory bronchiolitis is a lung disease associated with tobacco smoking. In pathology, it is defined by the presence of "smoker's macrophages". When manifesting significant clinical symptoms it is referred to as respiratory bronchiolitis interstitial lung disease (RB-ILD).

Diagnosis of respiratory bronchiolitis requires a correlation of clinical, radiologic and pathologic findings:

Respiratory bronchiolitis interstitial lung disease is respiratory bronchiolitis that manifests as a clinically significant interstitial lung disease. It is a form of idiopathic interstitial pneumonia associated with smoking.

It is a histological finding, not a pathological description. When associated with disease, it is known as "Respiratory bronchiolitis-associated interstitial lung disease" or "RB-ILD". Also, this disease is predominantly found in the upper lobe with centrilobar ground glass nodules. Importantly, no fibrosis is involved, just bronchial wall thickening. Treatment is to stop smoking.

The appearance is similar to desquamative interstitial pneumonia, and some have suggested that the two conditions are caused by the same processes.