In Parkinson's disease (PD), cognitive symptoms progressively worsen with disease progression and present a major clinical challenge that remains difficult to treat. Deep brain stimulation of the subthalamic nucleus (STN-DBS) is a widely used and clinically validated therapy for motor symptoms in PD; however, its cognitive effects remain underexplored. In this study, we examined how STN-DBS influences executive functioning, focusing on a well-established mental rotation task. In the task, patients were shown two images (reference, comparison) and were asked to decide whether the comparison image was rotated or mirrored. Twelve PD patients (6 women; mean age: 60 ± 10 years; mean disease duration: 12 ± 6 years) completed the task under two conditions: with therapeutic STN-DBS turned on and turned off. Behavioural cognitive performance was correlated with the volume of tissue activated, as determined by MR based electrode reconstruction. Results indicated that STN-DBS significantly improved mental rotation accuracy, suggesting a beneficial effect on visuospatial executive processing. Notably, stimulation involving limbic-associated regions of the right STN was associated with impaired performance, highlighting the relevance of stimulation site and its functional connectivity. Together, these findings contribute to the growing body of evidence that STN-DBS produces region-specific effects on distinct cognitive domains.