The occurrence of pneumatosis cystoides intestinalis (PCI) in the gastrointestinal tract is rare. Among the cases already documented in the English language literature, the association of PCI with jejunal diverticulosis has only been mentioned once or twice. We herein report a case of a 63-year-old woman who had both entities concurrently in a segment of the jejunum. What is important to note is the relationship of PCI to the diverticulosis and its possible pathogenesis. Through histological examination and review of related articles, we are convinced that a mechanical theory plays a pivotal role when both diseases occur in the same segment of intestine and are compounded by obstruction or impaired peristalsis. This finding, when properly applied to PCI in other settings, helps to resolve the pathogenesis of PCI and other related gas-filled cysts.