A lifting system for a furniture piece door oscillating around a horizontal axis comprises a support lever (9, 19) for the door (3, 7, 13) oscillating around an oscillation pin (10, 20) disposed on an inner side of a shoulder (12) of the furniture piece, a first elastic device (24) operatively connected to the support lever (9, 19) of the door (3, 7, 13) so as to provide a moment in the closing direction of the door (3, 7, 13) at the closed position of the door (3, 7, 13), and a primary moment in the opening direction of the door (3, 7, 13) starting from a partial opening position of the door (3, 7, 13), and a second elastic device operativamente connected to the shoulder (12) and the support lever (9, 19) so as to provide a force suitable for generating, relative to the oscillation pin (10, 20), an auxiliary moment in the opening direction of the door and/or respectively an opposing moment via friction against the support lever (9, 19) in the direction opposite to the movement of the door (3, 7, 13) along an arc of oscillation thereof around the maximum extension of the door (3, 7, 13) towards the furniture piece exterior.