Chest radiography is the most commonly performed imaging examination in paediatric patients with potential thoracic disorders. It remains the initial imaging study to evaluate most thoracic diseases in children. A systematic approach to the interpretation of paediatric chest radiographs, knowledge of basic radiological findings and consideration of clinical information, are the key to a correct radiological diagnosis. The normal mediastinum can have a variable appearance on radiographs, depending on the patient’s age, developmental stage, and health status and the anatomic variations of the thymus. Errors in interpretation may lead to inappropriate further imaging, incurring additional radiation exposure and cost. Obtaining a technically adequate chest radiograph in small children is particularly challenging due to their lack of cooperation. Potential pitfalls related to suboptimal images have to be considered.