BACKGROUND: Bronchiolitis is a heterogeneous group of disorders, each with its own clinical and radiographic presentation, treatment options, and prognosis. Until now, classifications were based on pathology and radiology. SUMMARY: Bronchioles are smaller than 2 mm in diameter and do not contain cartilage and mucous glands in their walls. Bronchiolitis is the term used to designate a disorder of the bronchioles and can have multiple etiologies. A specific diagnosis requires an extensive anamnesis, physical examination, pulmonary function testing, radiographic studies, and pathological investigation. We made a classification of bronchiolitis based on etiology, in order to give a diagnostic and therapeutic guidance. Further investigation is needed to optimize treatment for specific types of bronchiolitis. KEY MESSAGES: In this paper, a classification of bronchiolitis based on etiology is made. The paper provides in the diagnostic and therapeutic approach, although further investigation is needed to optimize treatment for specific types of bronchiolitis.