Background and Aim: Impairment in language content production, long-term memory and executive function in Parkinson's disease reported in several studies. Identification of these disorders is useful in planning for early interventions. The aim of this study was evaluation of semantic and phonemic clustering and switching in Parkinson's disease.

Methods: In this study, 30 patients with Parkinson's disease and 30 healthy individuals evaluated that were matched by age , sex and educational level . Clustering and switching average were compared between the two groups according to the Troyer method . Data recorded and analyzed using independent t test and Pearson correlation coefficient.

Results: Comparison of mean scores of clustering between patients with Parkinson's disease and healthy individuals indicated significant difference (p=0.05). In addition, significant difference was observed between mean score of switching in two groups (p=0.008).

Conclusion: The finding of the present study reveal that switching between semantic or phonemic subcategory and clustering impaired in patients with Parkinson's disease.