OBJECTIVES: To assess an influence of depression, dementia, disease severity and motor complications on the Quality of Life (QoL) in Parkinson's Disease (PD). METHODS: Quality of Life was measured in 241 patients with PD (male: 127, female: 114, mean age: 66.1 ± 7.5, duration of disease: 5.2 ± 3.2) using the Parkinson Disease Questionnaire (PDQ-39), a disease-specific instrument. Dementia was evaluated by using the MMSE and depression was evaluated by Hamilton Rating Scale (HAM). Disease severity and motor function were recorded with the Hoehn and Yahr scale and the UPDRS II-IV. Spearman's correlation coefficient was used to calculate correlation scores. RESULTS: All domains of PDQ-39 significantlty correlated with depressive symptoms. Significant correlation between HAM scores and PDQ-39 summary index (R=0.53, p <0.001) was observed. PDQ-39 also correlated with UPDRS II (R=0.67, p < .001), UPDRS III (R=0.49, p <0.001) and HY stage (R=0.62, p <0.001). Motor fluctuations and dyskinesias (UPDRS IV) had significant impact on QoL (R=0.57, p <0.001). Dementia or cognitive impairment had a minor correlation with UPDRS III and HY stage (R=-0.32, p <0.001 and R=-0.44, p <0.001, respectively) but had no correlation with PDQ-39. CONCLUSIONS: Disease severity, motor fluctuations, and depression influence on QoL in patients with Parkinson's disease. In contrast, a significant impact of cognitive impairment on QoL of patients with Parkinson's Disease was not revealed. Treatment of depressive symptoms and prevention of motor complications in PD patients may improve considerably their Quality of Life.