A device for grouping blanks (w1, w2) of smoking-article wrappers, coming one after another from a machine for treating said blanks, said device comprising a structure for receiving said blanks (w1, w2) having an inlet for said blanks coming from said treatment machine, and a collecting space, in communication with said inlet, for receiving said blanks and housing a group of said blanks (w1, w2) under formation, wherein said collecting space extends along a reference axis of said structure, said device also comprising at least one support (151, 1511, 15III, 15IV), which is movably mounted on said structure, for keeping the already-received blank or blanks in said collecting space close to said inlet and according to such an orientation that the lying plane of said blanks is transversal to said reference axis, wherein said at least one support (151, 1511, 15III, 151V) is movable along said reference axis for moving away the already-received blank or blanks from said inlet, and enabling reception of a new blank in said collecting space, wherein said at least one movable support (1511, 151V) comprises at least one belt-like support (1511, 15IV), which is movable along a ring-like closed path having a portion oriented along said reference axis, and wherein the portion (15'11, 15'IV) of said at least one belt-like support (1511, 151V) extending along said portion is configured to engage a lower side of the group of said blanks under formation, received within said collecting space, said device being characterized in that said belt-like support (1511, 151V) comprises one or more abutment portions (15IIB, 15IVB) configured to engage the front side of the blank that, in a given cycle of operation of said device, is first received in said collecting chamber, and for keeping said blank or the blanks that are received afterwards, in said orientation transversal to said reference axis. said device comprising a structure for receiving said blanks (w1, w2) having an inlet for said blanks coming from said treatment machine, and a collecting space, in communication with said inlet, for receiving said blanks and housing a group of said blanks (w1, w2) under formation, wherein said collecting space extends along a reference axis of said structure, said device also comprising at least one support (151, 1511, 15III, 15IV), which is movably mounted on said structure, for keeping the already-received blank or blanks in said collecting space close to said inlet and according to such an orientation that the lying plane of said blanks is transversal to said reference axis, wherein said at least one support (151, 1511, 15III, 151V) is movable along said reference axis for moving away the already-received blank or blanks from said inlet, and enabling reception of a new blank in said collecting space, wherein said at least one movable support (1511, 151V) comprises at least one belt-like support (1511, 15IV), which is movable along a ring-like closed path having a portion oriented along said reference axis, and wherein the portion (15'11, 15'IV) of said at least one belt-like support (1511, 151V) extending along said portion is configured to engage a lower side of the group of said blanks under formation, received within said collecting space, said device being characterized in that said belt-like support (1511, 151V) comprises one or more abutment portions (15IIB, 15IVB) configured to engage the front side of the blank that, in a given cycle of operation of said device, is first received in said collecting chamber, and for keeping said blank or the blanks that are received afterwards, in said orientation transversal to said reference axis.