The sense of well-being is central to the concept of quality of life (QoL), but there is not a universally accepted definition of health-related QoL. QoL refers to the patient's own evaluation of the impact of the disease. It includes physical, psychological and socioeconomic dimension, and its measurement is of paramount importance in evaluating research outcomes and in cost-benefit analyses. In addition, QoL assessment helps to identify problems and may be essential in chronic and disabling diseases such as in Parkinson's disease (PD). There are numerous reasons for the decrease in QoL suffered by PD patients: restrictions in mobility, falls, emotional disorders, social embarrassment, isolation, sleep disturbances, dyskinesias, and fluctuations. Many aspects of these disorders go unnoticed in clinical evaluation, and only QoL assessment allows them to be rated. Generic instruments have been used in a few studies measuring QoL in PD patients. Only recently have specific instruments as PDQ-39 and PDQL-37 been designed and validated. QoL assessment in PD is an important and expanding area, with a promising application in clinical trials and pharmacoeconomics.