In the present work, a very compact reaction system thermally integrated for the distributed hydrogen production by natural gas reforming is reported. The system is based on hydrocarbon Auto-Thermal Reforming, followed by a Water-Gas Shift module. A compact heat exchanger was placed between the two catalytic stages, in order to assure an appropriate thermal integration that avoid any other external heat duties. Experimental results demonstrated that the integrated configuration allowed short start-up time, since the system reached the thermal regime in less than 3 minutes, and assuring a relevant hydrogen production in very short time. Preliminary tests showed very impressive performances of the system. Despite a quite slow WGS stage, the p...