Retractable screen and keyboard assembly for tables, comprising: - a supporting structure provided with a frame defining a housing, and with a supporting frame for leaning on a table; - the screen being able to rotate from a stowed position in which it is stowed inside the housing and flush with the supporting frame to an elevated use position, - a platform arranged in the housing on which the keyboard rests, - means for guiding the platform vertically from a lower position which leaves space for the stowed screen and an upper use position, wherein it comprises a base for the screen which can rotate about a first fixed axis (Γ) in relation to said frame, the screen being mounted on said base, enabling the assembly of screen and base to rotate about said first fixed axis (Γ) from the stowed position to the elevated use position, wherein the assembly comprises an operating mechanism provided with: at least four cams (8, 9, 10, 11) for pushing the platform, two on each side and below the platform which can rotate in relation to the corresponding axes in relation to the frame; two first braces (12, 13) of connection between the base and the two closest cams (8, 9), and the operating mechanism being able thereby to be actuated by a single motor; characterized in that: the base, each of the braces (12, 13) and the respective cam (8, 9) forming an articulated quadrilateral so that the rotation of the base causes the rotation of the two closest cams (8, 9); and two second braces (14, 15) of connection between the two closest cams (8, 9) and the two furthest cams (10, 11), each of the two closest cams (8, 9), the corresponding furthest cam (10, 11) and the corresponding brace (14, 15) forming an articulated parallelogram so that the four cams (8, 9, 10, 11) have the same motion and simultaneously push the platform in a vertical movement. - a supporting structure provided with a frame defining a housing, and with a supporting frame for leaning on a table; - the screen being able to rotate from a stowed position in which it is stowed inside the housing and flush with the supporting frame to an elevated use position, - a platform arranged in the housing on which the keyboard rests, - means for guiding the platform vertically from a lower position which leaves space for the stowed screen and an upper use position, at least four cams (8, 9, 10, 11) for pushing the platform, two on each side and below the platform which can rotate in relation to the corresponding axes in relation to the frame; two first braces (12, 13) of connection between the base and the two closest cams (8, 9), and the operating mechanism being able thereby to be actuated by a single motor; characterized in that: the base, each of the braces (12, 13) and the respective cam (8, 9) forming an articulated quadrilateral so that the rotation of the base causes the rotation of the two closest cams (8, 9); and two second braces (14, 15) of connection between the two closest cams (8, 9) and the two furthest cams (10, 11), each of the two closest cams (8, 9), the corresponding furthest cam (10, 11) and the corresponding brace (14, 15) forming an articulated parallelogram so that the four cams (8, 9, 10, 11) have the same motion and simultaneously push the platform in a vertical movement. the base, each of the braces (12, 13) and the respective cam (8, 9) forming an articulated quadrilateral so that the rotation of the base causes the rotation of the two closest cams (8, 9); and two second braces (14, 15) of connection between the two closest cams (8, 9) and the two furthest cams (10, 11), each of the two closest cams (8, 9), the corresponding furthest cam (10, 11) and the corresponding brace (14, 15) forming an articulated parallelogram so that the four cams (8, 9, 10, 11) have the same motion and simultaneously push the platform in a vertical movement.