When working with cable-driven parallel robot, the placement of exit points greatly affects its performance, such as workspace and cable tensions. This work focuses on a robotic rehabilitation device for upper limb based on a parallel mechanism driven by cables. In particular, the aim of this work is to identify the optimal placement of the exit points to minimize the cable tensions, thus the required actuator torque. A kinematic and dynamic model of the proposed design is presented to properly describe the mechanism behavior and identify the optimal motor placement.