The PDQ-39 and PDQL were simultaneously applied to 187 PD patients. Additional assessments included Hoehn and Yahr staging, Schwab and England Scale (SES), Unified Parkinson's Disease Rating Scale, Pfeiffer's Short Portable Mental Status Questionnaire (SPMSQ) and Hospital Anxiety and Depression Scale (HADS). Criteria for acceptability, scaling assumptions, reliability, construct validity and precision were drawn up.