AIM OF THE STUDY: This study aimed to analyze the most established genetic causes of Parkinson's disease (PD) in a cohort of patients from Czechia. CLINICAL RATIONALE FOR THE STUDY: PD is the second most common neurodegenerative disorder, with both genetic and environmental factors contributing to its pathogenesis. MATERIAL AND METHODS: We examined 214 patients with PD and 186 controls. Each patient underwent an examination using the Montreal Cognitive Assessment to assess the severity of cognitive impairment. Genetic analysis was performed using next- -generation sequencing and multiplex ligation-dependent probe amplification, focusing on mutations in GBA1, LRRK2, PINK1, PRKN, and SNCA genes. RESULTS: Clinically relevant mutations in GBA1 (pathogenic/likely pathogenic or severe/mild/risk variants) were the most frequently observed variants (n = 30; 14.0% of the PD cohort in total), including both known pathogenic mutations and the mild risk allele p.Glu365Lys (n = 12; 5.6% of cases), which was associated with earlier disease onset. Pathogenic mutations were also detected in LRRK2 (n = 2; 0.9%), SNCA (n = 1; 0.5%), and compound heterozygous mutations in PRKN (n = 2; 0.9%). Carriers of heterozygous mutations in PRKN were equally represented in patients and controls. No pathogenic PINK1 mutations were identified. Cognitive impairment was not significantly more frequent in GBA1 mutation carriers (p = 0.320). A positive family history of PD was more common in patients than in healthy controls (n = 51; 24% vs. n = 6; 3%, p < 0.001). CONCLUSIONS AND CLINICAL IMPLICATIONS: Our findings highlight notable genetic variability in Czech PD patients, particularly involving GBA1 mutations. However, these variants were not associated with early cognitive decline. The study underscores the value of genetic screening in PD and the need for further research into genotype-phenotype correlations.