There has been designed a device for verticalization and aiding the gait of individuals suffering from paresis of the lower limbs. It can be counted in the category of so-called “wearable robots”, whose task is to replace or aid human limbs. Dependently on the function realized, these robots are classified into one of the following three groups: a) exoskeletons - strengthening the force of human muscles beyond their natural abilities, b) orthotic robots - restoring lost or weakened functions of human limbs, c) prosthetic robots - replacing an amputated limb. A significant feature of the device that has been designed is the fact that it has not to replace human limbs, but only restore them to their lost motor capabilities. Thus, according to the presented classification, it is an orthotic robot. Unlike in the case of the existing systems for verticalization, the gait is to be realized in a way that is automatic to the highest possible extent, keeping the user involved as little as possible, and the device is to imitate the natural movements of man with the highest fidelity. Within the works on the system for verticalization and aiding the motion, a simulation model of the device was created. It includes a structure of the robot, a model of the actuators and a model of the human body that constitutes the load for the driving units. Then, simulation studies were carried out, including evaluation of the power demand of the device as well as the influence of the gait rate and of the length of the steps on the operation of the system.