In Parkinson's disease, gait disturbances represent one of the most disabling motor symptoms, frequently associated with an increased risk of falls, loss of independence and a negative impact on quality of life. Patients with Parkinson's Disease, display an abnormal gait pattern (reduced gait speed, shortened stride length, and a longer double-limb support phase) and they are typically unable to generate a proper stride length and to maintain a steady gait rhythm. Therefore, improving gait ability is a primary goal of physical therapy in patients with Parkinson's Disease. Conventional Physiotherapy aimed at enabling patients to maintain their maximum level of activity and independence is often prescribed, but treatments for gait give only limited benefits. Promising reports have suggested that external sensory cueing (acoustic, visual, verbal cues), through an attention mechanism, may help to increase the deficient internal cueing in Parkinson's Disease, thus improving gait pattern.Treadmill training, which induces a constant horizontal movement, generates a rhythmic input for locomotion, coordinating the upper and lower limbs, offering a useful retraining modality that complements conventional therapy. In the last decade some researchers focused on the use of partial body weight support systems on the ground or with the combination of treadmill training (Body weight support-treadmill). These systems, which improves the ability to stand in an upright position with a redistribution of forces on the trunk, thus disengaging the girdle and upper limbs, suggests a greater improvement in motor performance and walking ability compared with conventional phisiotherapy. In recent years, the interest in automated robotic devices for gait training for Parkinson's Disease patients has grown. With their consistent, symmetrical lower-limb trajectories, robotic devices provide many of the proprioceptive inputs that may increase cortical activation and improve motor function while minimizing the intervention of a therapist. Moreover, proprioceptive inputs may share mechanisms that are common to external cues, thus stimulating the cerebellar-premotor pathway to improve gait. Besides,the preprogrammed walking pattern corresponds to normal gait kinematics including: gait cycle timing, inter-limb and inter-joint coordination, appropriate limb loading, and afferent signaling. A recent randomized controlled trial that compared a comprehensive rehabilitative program vis-à-vis robot-assisted gait training has shown that the latter displays some advantages. A pilot, non-controlled study explored the effect of robot-assisted gait training on freezing of gait.Still, despite recent interest in automated locomotion training, there is still very little evidence to support the superiority of this technique over traditional gait training. A computerized gait analysis represents an useful aid to study gait disturbances. The analysis sets objectives and defines quantitative data about gait changes occurred in a patient, in relation to the progression of underlying disease or th effectiveness of treatments administered (medication, surgery or physical). So the main aim of this study will be to analyze, through a clinical and an instrumental evaluation, the effectiveness of a Lokomat gait training in subjects affected by Parkinson's disease in comparison to a ground conventional gait training