Abstract: A box (1) for a pack of cigarettes has the shape of a hollow body dimensioned to receive a pack of cigarettes, the hollow body being delimited by at least four surfaces (2, 3, 4, 5) forming the walls of the body and a surface (6) forming a bottom constituted by a prolongation of one wall of the body and connected to that one wall by a bend line (7). The surface (6) forming the bottom of the body is prolonged by a flap (8) connected to the surface forming the bottom by a bend line (9) permitting positioning substantially at a right angle the flap relative to the surface (6) forming the bottom. The flap (8) has the form of a flexible dihedral with at least two legs (8A, 8B) of variable geometry, at least one (8B) of the legs (8A, 8B) of the dihedral being inserted within the body between a wall (17A) of the pack of cigarettes (17) and a wall (5) of the box so as to maintain the surface (6) forming the bottom of the body in closed position of the body.