To identify the demographic factors, impairments and activity limitations that contribute to health-related quality of life (HRQOL) in people with idiopathic Parkinson s disease (PD). Method: Two hundred and ten individuals with idiopathic PD who participated in the baseline assessment of a randomized clinical trial were included. The Parkinson s Disease Questionnaire-39 summary index was used to quantify HRQOL. In order to provide greater clarity regarding the determinants of HRQOL, path analysis was used to explore the relationships between the various predictors in relation to the functioning and disability framework of the International Classification of Functioning model. Results: The two models of HRQOL that were examined in this study had a reasonable fit with the data. Activity limitations were found to be the strongest predictor of HRQOL. Limitations in performing self-care activities contributed the most to HRQOL in Model 1 (? = 0.38; p <0.05), while limitations in functional mobility had the largest contribution in Model 2 (? = -0.31; p <0.0005). Self-reported history of falls was also found to have a significant and direct relationship with HRQOL in both models (Model 1 ? = -0.11; p <0.05; Model 2 ? = -0.21; p <0.05). Conclusions: Health-related quality of life in PD is associated with self-care limitations, mobility limitations, self-reported history of falls and disease duration. Understanding how these factors are inter-related may assist clinicians focus their assessments and develop strategies that aim to minimize the negative functional and social sequelae of this debilitating disease.