A method of forming groups of cigarettes on a packing machine, whereby a conveyor feeds a succession of pockets in steps past a number of group-forming stations, where the pockets receive respective groups of cigarettes fed axially to the relative pockets by means of independent pushers, which are operated in a normal cyclic operating sequence to move selectively through respective group-forming stations; and whereby the formation of a gap along the conveyor, caused by non-supply of a faulty group to a relative pocket, is prevented by replacing the normal cyclic operating sequence with a different cyclic sequence capable of ensuring all the pockets are filled as of the fully operative group-forming stations only.