Idiopathic pulmonary fibrosis (IPF) has a more variable clinical course than has been traditionally recognised. Many patients will remain stable over time while others experience relatively rapid deterioration. The prognosis and clinical course of patients with other fibrosing lung diseases is also variable. A number of conditions may complicate the clinical course of the idiopathic fibrosing lung diseases, which results in morbidity and mortality, but also represents potentially treatable causes of worsening symptoms. Infection and malignancy have a long-recognised association with IPF while other conditions, particularly pulmonary hypertension and acute exacerbation of IPF, are being increasingly recognised in this patient population. Many of these patients have serial high-resolution CT (HRCT) examinations that may demonstrate one or more of these supervening conditions. In this article we review the more common conditions that may complicate the course of idiopathic fibrosing lung disease with an emphasis on the HRCT appearance, which the reporting radiologist should be aware of.