On the basis of one case of colonic sub-mucosal cystic pneumatosis explored by double contrast enema, the authors emphasise the pathognomic diagnostic value of the "puzzle" appearance. This appearance is made by precise adaptation of the opaque colonic mucosa depressed in the form of a "cupola" over the intraparietal gas bubble which results in the deformity. Endoscopy failed to reveal the disorder in the case reported here.