PURPOSE To determine the factors associated with poor quality of life (QoL) in patients with idiopathic Parkinson's disease (PD) in a clinic-based sample. SCOPE One hundred patients were included in this study. To assess the quality of life the Parkinson's Disease Questionnaire (PDQ-39) was used. A structured questionnaire interview and a complete neurological examination, including the Hoehn and Yahr scale (H-Y), the Schwab and England disability scale, II, III, IV parts of the unified Parkinson's disease rating scale (UPDRS part II, III, IV), Montgomery-Asberg depression rating scale (MADRS) and the Mini-Mental state examination (MMSE) were performed. RESULTS AND CONCLUSIONS The most important predictive factor was MADRS score, followed by clinical fluctuations as measured by UPDRS part IVB and the H-Y stage of disease, which account for 79% of the variance of QoL scores. Therefore, recognition of depression should become an important part of treatment of PD.