A pulsion diverticulum of the mid-thoracic oesophagus was resected because of severe dysphagia. A subdiverticular myotomy was associated for the treatment of non-propagated oesophageal contractions, without oesophageal low-sphincter abnormalities. Three months post-operatively, the dysphagia was still present and manometry showed the absence of lower sphincter relaxation after 45 percent of deglutitions; a lower oesophageal sphincter myotomy was performed, resulting in correction of the dysphagia and of the sphincter relaxation abnormalities. The deficit of the inhibitory nervous mechanism, responsible for abnormalities of lower oesophageal sphincter relaxation, was present in the entire intramural oesophageal plexus, but, was not symptomatic at the level of the IOS prior to resection of the diverticulum.