Pulmonary fibrosis (PF) is a very rare condition in children, which may be observed in specific forms of interstitial lung disease. None of the clinical, radiological, or histological descriptions used for PF diagnosis in adult patients, especially in situations of idiopathic PF, can apply to pediatric situations. This observation supports the view that PF expression may differ with age and, most likely, may cover distinct entities. The present review aims at summarizing the current understanding of PF pathophysiology in children and identifying suitable diagnostic criteria.