Arrangement for storing items, comprising a loading station, a storage structure and an unloading station, wherein said storage structure comprises a plurality of vertical racks (32, 34, 36, 38, 40, 42, 44, 46, 44', 46'), each comprising at least a pair of vertical walls arranged parallel and facing and provided, at least on the faces facing each other, with a plurality of supports, arranged at different heights and adapted to receive removable supporting elements (12, 14) carrying said items to be stored, wherein said removable supporting elements are made in the form of trays or drawers (12, 14), each of which can be inserted into and removed from the supports of a pair of facing vertical walls of one of said vertical racks (32, 34, 36, 38, 40, 42, 44, 46, 44', 46'), each removable supporting element, once inserted on respective supports of said facing vertical walls of one of said vertical racks, defining with said vertical walls a compartment for storing an item, each removable supporting element (12,14) being adapted to carry a single item and each compartment being consequently adapted to store a single item, and said storage structure comprises at least two vertical rack groups (32, 34, 36, 38, 40, 42, 44, 46, 44', 46'), wherein the distance between said vertical walls arranged parallel to and facing each other of the vertical racks of one of said vertical rack groups is different from the distance between said vertical walls arranged parallel to and facing each other of the vertical racks of another one of said vertical rack groups characterized in that said storage arrangement comprises a sensor system for determining the size of an item to be stored, at least two dimensions of the item in directions perpendicular to each other being taken into account in determining the space in which the item is to be stored, and a control system provided with a memory unit in which the geometry of said storage structure and the arrangement of the items already present in said storage structure are memorized, and arranged to determine, based on the output of said sensor system and the data contained in said memory unit, in which vertical rack and on which supports of said vertical rack to place said item to be stored. and said storage structure comprises at least two vertical rack groups (32, 34, 36, 38, 40, 42, 44, 46, 44', 46'), wherein the distance between said vertical walls arranged parallel to and facing each other of the vertical racks of one of said vertical rack groups is different from the distance between said vertical walls arranged parallel to and facing each other of the vertical racks of another one of said vertical rack groups characterized in that said storage arrangement comprises a sensor system for determining the size of an item to be stored, at least two dimensions of the item in directions perpendicular to each other being taken into account in determining the space in which the item is to be stored, and a control system provided with a memory unit in which the geometry of said storage structure and the arrangement of the items already present in said storage structure are memorized, and arranged to determine, based on the output of said sensor system and the data contained in said memory unit, in which vertical rack and on which supports of said vertical rack to place said item to be stored.