A folding door storage system for an opening of a closet including a first door panel and a second door panel, which panels are pivotal with respect to one another, and a carrier arrangement which can be moved, in a folded state of the door panels in which they are aligned parallel with one another, together with the door panels into a storage space. In order to achieve a safe guiding and moving of the door panels and in order to be able to use the system also for very large dimensions, the first door panel is mounted for movement transversely with respect to the front side of the closet on a guide rail by means of a guide element, wherein the guide element, in the folded state of the door panels, can be transferred into a second guide rail arranged parallel with respect to an outside wall of the closet. A locking mechanism is mounted on the carrier arrangement, which locking mechanism prevents unintended movements and swivellings of the door panels.