AimPneumomediastinum is an uncommon condition with differential diagnoses of very different prognosis. The aim of the present study was to retrospectively review patients who presented with pneumomediastinum, and to look for salient features on presentation to establish the difference between benign spontaneous pneumomediastinum (SPM) and oesophageal perforation (Boerhaave's syndrome) on presentation.Patients and MethodsFrom 1 July 1999 to 30 June 2013, 163 cases of pneumomediastinum, excluding those with trauma and procedure‐related episodes, presented through the Accident and Emergency Department to the Hospital Authority hospitals in the New Territories East Cluster. There were 142 SPM cases, and 21 were oesophageal perforations.ResultsPresenting features, hospital stay and outcomes were analysed. Fever at presentation (P = 0.030), history of vomiting (P = 0.028), pneumothorax on initial chest radiograph (CXR) (P = 0.044) and age ≥ 28 years (P = 0.021) were found to be independent predictors for non‐SPM diagnoses.ConclusionSPM is still more common than oesophageal perforation in those without any history of trauma or recent instrumentation, and runs a benign course. However, the presence of fever, a history of vomiting, pneumothorax on initial CXR and patient age over 28 years should mandate further investigations to rule out more sinister diagnoses and to administer appropriate management.