The objective of this study was to illustrate the wide spectrum of subcutaneous emphysema in the emergency room; to show the key findings on computed tomography, plain radiographs, and echography; and to discuss the differential diagnoses. Subcutaneous emphysema is a common finding in emergency department imaging studies. It has a great importance due to its broad casualty, some of them totally benign, but others potentially lethal. We retrospectively reviewed our database of emergency pathology, analyzing its origins and associated features. SE was associated to traumatic, iatrogenic, or infectious causes (necrotizing fasciitis, Fournier gangrene). It also was found associated with thoracic (causing pneumothorax and pneumomediastinum) and abdominal pathology related to intraperitoneal and retroperitoneal gas. Diagnostic difficulties and differential diagnoses are emphasized. Radiologists must be aware of abnormal gas in soft tissue because it may be the main or unique sign leading to an underlying pathology, which can be lethal.