In this paper we present new design approaches for the positional accuracy improvement of the 4-DOF parallel manipulator PAMINSA. The particularity of this manipulator is the decoupling of displacements in the horizontal plane from its translation along the vertical axis. The positioning errors caused by the inclination of the platform relating to the base are cancelled by means of two different approaches. The first solution is realized by means of two correcting systems mounted on the drive system of the vertical displacements. The second solution is carried out by a correcting mass mounted on the platform. The suggested solutions are illustrated by the numerical examples and the performances of such a design are shown.