INTRODUCTION: Virtual reality (VR) has become increasingly popular for rehabilitation in people with Parkinson's disease (PD). Despite studies already showing positive effects of prolonged VR interventions, there have been little investigations on the effects of VR on the movement execution, which might impact training intensity. The aim of this study was to investigate the effect of VR on movement execution compared to therapist instructed (TI) exercises in people with PD. METHODS: Thirty people with PD performed three different exercises aimed at improving range of motion (ROM) or postural control in an immersive VR setting. Comparable TI exercises were conducted. ROM and center of pressure were analyzed with a marker-based motion capture system and a pressure plate, respectively, to quantify movement execution. Statistical analysis of was performed using one-way Anova with Bonferroni correction for multiple comparisons and Cohen's d was calculated as effect size. RESULTS: For the two exercises to increase ROM results were inconsistent as one exercise showed larger ROM for the VR condition (p = 0.009, d = 0.895), whereas the other showed larger ROM during the TI condition (p < 0.001, d = 1.955). For the weight-shifting exercise we showed larger and faster displacements of the center of pressure for the TI exercise (p < 0.05, d > 0.5). DISCUSSION: This study demonstrates that the effects of VR on exercise execution differ depending on the specific exercise goal and task characteristics. While fully immersive VR was associated with greater ROM in exercises that benefit from continuous visual feedback, conventional TI exercises resulted in superior performance for other tasks, including balance exercises targeting limits of stability. The findings suggest that visual feedback, perceived safety, and task-specific demands play a crucial role in determining the effectiveness of VR-based interventions. Future research should focus on optimizing VR interventions through adaptive feedback and personalized task difficulty to fully exploit their potential in therapeutic exercise settings.