Chronic pulmonary aspiration (CPA) in children is an important cause of recurrent pneumonia, progressive lung injury, respiratory disability and death. It is sporadic, intermittent and variable, and often occurs in children with complicated underlying medical conditions and syndromes that produce symptoms indistinguishable from CPA. For most types of aspiration there is no gold-standard diagnostic test. The diagnosis of CPA is currently made clinically with some supporting diagnostic evaluations, but often not until significant lung injury has been sustained. Despite multiple diagnostic techniques, the diagnosis or exclusion of CPA in children is challenging. This is of particular concern given the outcome of unrecognised progressive lung injury and the invasiveness of definitive therapies. Although new techniques have been introduced since the 1990s and significant advances in the understanding of dysphagia and gastro-oesophageal reflux have been made, characterisation of the aspirating child remains elusive.