The aim of this study was to compare motor recovery in subacute and chronic stroke patients through clinical assessment scales and a set of kinematic parameters recorded using a robotic system. Fifty post-stroke patients, 25 subacute and 25 chronic, and 20 healthy subjects participated in this study. The InMotion 2.0 robotic system for shoulder/elbow rehabilitation was used. Clinical outcome measures were used for assessment. Kinematic parameters related to the speed measured at the robot's end effector and to the movement's smoothness were computed. The results of this study show that the robot-assisted training can contribute to reduce motor impairment in both subacute and chronic stroke patients. The evaluation of the kinematic parameters and their correlation with the clinical scales highlight some differences in mechanisms of recovery in subacute and chronic stroke patients. The proposed set of kinematic parameters and the analysis of the reaching movements' onset time, associated with a quantitative evaluation of motor improvement provided by the clinical outcome measures, are also able to quantify the changes in the quality of motion obtained after robot-assisted therapy in stroke patients. The higher gain in the subacute stroke patients suggests that the rehabilitative treatment provided at an earlier stage is able to avoid the development of pathologic patterns, resulting in a better quality of motion.