Support and actuation device for coplanar sliding doors, in particular for floor and hanging wardrobes, also of reduced sizes, adapted to determine the support and the actuation and sliding of the doors in alternate longitudinal directions in positions coplanar to each other, wherein the doors are actuated from a closed position thereof, in which they are aligned with respect to the wardrobe front face, to an opened position thereof in which they are at first displaced forward and then are let to slide laterally in the desired position thereof, parallel to the plane of the wardrobe front face, and vice versa, the wardrobe comprising at least two flat front doors, a rear wall, an upper flat ceiling, a flat lower bottom and two side walls (11, 12), the support and actuation device being substantially constituted by a first group of upper component parts applied in use on to the flat ceiling and secured with their upper part to the rear wall of the relative door, and by a second group of lower component parts, applied in use on to the flat bottom of the wardrobe and fixed with their lower part to the rear wall of the relative door, said first group comprising a load-bearing rectilinear section bar fixed below the flat ceiling, and said load bearing section bar co-operating with movable means (23,24,25) of the support and actuation device, adapted to support a relative door and to displace the same in the longitudinal and transversal directions of the same load bearing section bar, from a closing to the opening position of the same door, and vice versa, while said second group being comprising a rectilinear guide section bar secured below the flat bottom and shaped as a horizontal sliding guide member, formed preferably by at least an horizontal wing, and co-operating with stationary guide members (30, 31) and movable guide members (32, 33), adapted to drive the sliding of the relative door in the longitudinal direction of said guide section bar and transversal direction in the direction of the wardrobe depth, characterized in that said load-bearing section bar is shaped with a U-shape in the direction of the depth of the wardrobe, in such a way to define a central flat portion, with a width smaller than the depth of the wardrobe, and two short flat portions, respectively front and rear portions,which are joined orthogonally to the end portions of the central flat portion, of which the front flat portion is provided with two side notches (19, 20), identical and spaced away to each other along the same portion in correspondence of the relative front door, and along the central flat portion there are fixed, in correspondence of each door, a respective side wall and a respective central side wall, which are all identical to each other, of which the side walls are secured to the free end portions of the central flat portion, whereas the central side walls are secured in an approached and parallel position to each other into the area comprised between the side notches (19, 20) adjacent to each other, under the condition in which between each pair of side walls (21, 22) a flat path is defined for the sliding of the relative door in the longitudinal and transversal directions, and each of said side and central walls is constituted by a relative piece (34, 35), shaped with a correspondent longitudinal flat edge (36, 37), which is depressed with respect to the upper side (38, 39) of the relative piece, and a respective end-of-stroke block (40, 41) of said movable means (23, 24, 25) is fixed on to each one of said flat edges, wherein each pair of end-of-stroke blocks (40, 41) is associated with a door, and each one of the end-of-stroke blocks (40, 41) is larger than the thickness of the respective flat edge (36, 37) of the side wall part to which it is fixed, in a manner to be protruded slightly inward of said load bearing section bar, and to act so as an end-of-stroke abutment surface of the correspondent said movable means (23,24,25), wherein the two end-of-stroke blocks (40, 41) delimiting the longitudinal sliding stroke of said movable means of each door are fixed on to the relative side wall part in positions offset to each other, and with this arrangement of the different end-of-stroke blocks, therefore, into the free space defined between the respective internal flat edges (44,45) of the blocks (40, 41), fixed in the central position of said load bearing section bar, and the opposite front flat portion of the same load bearing section bar, there may slide in the alternate longitudinal direction said movable means (24, 25) of each door, when these latter do not interfere with these central blocks, in the extracted position of the same door, and under this condition it is possible to displace singularly each door of the wardrobe from its closing position, in which it is re-entered inward the wardrobe and its movable means (24, 25) are abutting to the relative blocks, to its opening position in which it is displaced in the extracted position, and its movable means do not interfere with the same blocks, and characterized in that said movable means (23, 24, 25) are constituted by a torsion bar and by at least two sliding lateral trucks (24, 25), identical to each other and co-operating with the relative end portion of said torsion bar as well as supporting the correspondent support elements of a relative door, said torsion bar of each door being supported at its end portions by said sliding trucks (24, 25) of the same door for determining the transversal sliding of the same trucks, from the one to the other one of the closed and opened position of the relative door.