Bronchiolitis is a nonspecific inflammation of the respiratory bronchioles and peribronchiolar alveolar sacs that has variable causes, clinical manifestations, and evolution. However, suggestive, specific diagnoses are rarely made based on clinical history alone. As both CXR and PFT findings are also frequently nonspecific, a high index of clinical suspicion should be maintained in order to diagnose and/or exclude bronchiolar disease. Given these limitations, in our experience, HRCT scanning may play a critical role in both suggesting specific causes of bronchiolar disease and directing optimal management in select cases. Tree-in-bud opacities, for example, typically signify an infectious cause with a pattern of distribution often suggestive of particular causes, including Mycobacterium tuberculosis, atypical mycobacterial infection, CF, and ABPA. Even when nonspecific in appearance, as typically occurs in AIDS, the finding of tree-in-bud opacities is often sufficiently specific for infection to suggest empirical treatment obviating biopsy. Poorly defined centrilobular ground-glass nodules commonly indicate subacute HP in a nonsmoker, whereas RB/RB-ILD and PLCH are typically seen in smokers. In select cases, these findings, coupled with appropriate clinical history and serologic testing, also may obviate more invasive diagnostic testing. In distinction, other causes of centrilobular nodules usually require open lung biopsy rather than transbronchial biopsy for definitive diagnosis. Finally, mosaic attenuation is characteristically associated with constrictive bronchiolitis. It is anticipated that the application of the algorithmic approach presented in this article will facilitate the timely diagnosis and/or optimal management of bronchiolar disorders that may otherwise be difficult to identify. In many cases, a diagnosis may be made solely using HRCT scans in combination with the history and clinical presentation.