A mechanism for moving coplanar doors of a piece of furniture, said mechanism comprising at least one moving unit (10, 10') for moving a respective door (101, 102) of said piece of furniture, said at least one moving unit (10, 10') comprising: - a connection bracket adapted to be connected to said respective door (101, 102); - a supporting member in form of a main carriage which supports said bracket, said supporting member being mobile along a longitudinal direction defined by longitudinal guiding means (5',5") connectable to said piece of furniture, - a guiding member of said connection bracket for guiding the movement of said connection bracket between a first and a second operating position characteristic of a coplanar door condition and of parallel, non-coplanar door condition, respectively, said guiding member and said connection bracket respectively comprise first guiding means and second guiding means, which interact to guide said connection bracket between said first and said second operating position, wherein said guiding member is stably connected with said piece of furniture during the movement of said connection bracket between said first and second operating position, and wherein said guiding member is stably connected with said connection bracket when the same reaches said second operating position, said supporting member being movable relative to said guiding member along said longitudinal direction during the movement of said connection bracket between said first and said second operating position, wherein the movement of said connection bracket relative to the guiding member and to the supporting member is a roto-translation defined by said interaction of said first and second guiding means, the first guiding means comprising curve-shaped guiding grooves (71, 72), and wherein said mechanism comprises coupling/releasing means of said guiding member to/from said piece of furniture configured for coupling said guiding member to said piece of furniture during the movement of said connection bracket (40, 140) between said first and said second operating position, and configured for releasing said guiding member from said piece of furniture when said connection bracket (40, 140) occupies said second operating position. - a connection bracket adapted to be connected to said respective door (101, 102); - a supporting member in form of a main carriage which supports said bracket, said supporting member being mobile along a longitudinal direction defined by longitudinal guiding means (5',5") connectable to said piece of furniture, - a guiding member of said connection bracket for guiding the movement of said connection bracket between a first and a second operating position characteristic of a coplanar door condition and of parallel, non-coplanar door condition, respectively, said guiding member and said connection bracket respectively comprise first guiding means and second guiding means, which interact to guide said connection bracket between said first and said second operating position, wherein said guiding member is stably connected with said piece of furniture during the movement of said connection bracket between said first and second operating position, and wherein said guiding member is stably connected with said connection bracket when the same reaches said second operating position, said supporting member being movable relative to said guiding member along said longitudinal direction during the movement of said connection bracket between said first and said second operating position, wherein the movement of said connection bracket relative to the guiding member and to the supporting member is a roto-translation defined by said interaction of said first and second guiding means, the first guiding means comprising curve-shaped guiding grooves (71, 72), and wherein said mechanism comprises coupling/releasing means of said guiding member to/from said piece of furniture configured for coupling said guiding member to said piece of furniture during the movement of said connection bracket (40, 140) between said first and said second operating position, and configured for releasing said guiding member from said piece of furniture when said connection bracket (40, 140) occupies said second operating position.