INTRODUCTION: Deep brain stimulation (DBS) is an increasingly popular therapeutic method for treating motor symptoms in Parkinson's disease, but its impact on non-motor symptoms in long-term follow-up remains debated. METHOD: The primary objective of this study was to monitor the cognitive functioning, mood, and quality of life in 2 years of unilateral and staged bilateral subthalamic nucleus DBS. A cohort of 30 patients was evaluated at three intervals: before DBS surgery, at 6 months, and 24 months post-surgery. The time points of neuropsychological assessments were set to control the impact of unilateral and bilateral DBS throughout the treatment. Two selected groups, unilateral and bilateral DBS, were also analyzed. The study employed a combination of computerized and paper-based tests to assess cognitive functions, alongside questionnaires to gauge emotional state and quality of life. The cognitive evaluation focused on three domains critical for daily activities: attention and processing speed, learning and episodic memory, and executive functions, including working memory and cognitive flexibility. RESULTS: Analysis of the entire cohort from baseline through the two follow-up assessments revealed no decline in cognitive function, mood, or quality of life, alongside significant motor improvement. Additional analyses of the two subgroups-unilateral DBS and staged bilateral DBS-also showed no overall decline in any assessed domain over the 2-year follow-up period. However, comparison of cognitive outcomes with normative data indicated a higher proportion of patients meeting criteria for cognitive decline at the 24-month follow-up in the staged bilateral DBS group compared with the unilateral DBS group. CONCLUSION: The findings support the long-term overall stability of cognitive function, mood, and quality of life following unilateral and staged bilateral subthalamic DBS. Subgroup analyses did not reveal any significant decline in cognitive measures over time. Nevertheless, individual comparisons with normative data showed a higher proportion of patients with memory deficits in the staged bilateral DBS group after the two-year follow-up.