The role of computed tomography (CT), including high-resolution computed tomography (HRCT), is still evolving in children. Radiation dose is an important consideration, but CT has advantages over chest radiography as it is more sensitive and specific for a variety of conditions affecting the pulmonary parenchyma. Careful attention to CT technique is vital for good quality diagnostic images in the paediatric population. The CT appearances of bacterial, viral, fungal, tuberculous and mycoplasma respiratory tract infections are discussed. The role of CT in specific circumstances such as the investigation of complicated bacterial pneumonia, the immunocompromised child and the sequelae of respiratory infections is addressed.