OBJECTIVES: To evaluate the psychometric properties of the Symptom Severity in Parkinson's Disease Scale (SSPDS), a new developed Parkinson's disease (PD) specific patient-reported outcome (PRO) measure reflecting the patients' perspective on their motor and non-motor symptoms. METHODS: Data were analyzed from a cross-sectional, community-based sample of 235 patients with idiopathic PD, who completed a set of standardized questions including the SSPDS, the short-form Parkinson's Disease Questionnaire (PDQ-8) and the EQ-5D. RESULTS: Confirmatory factor analysis confirmed six factors: four factors of health status ("bodily discomfort", "mobility", "cognitive functioning" and "emotional well-being"), one factor for the total health status, and one of non-motor symptoms worsened by ADRs (ADR_NMS score). The 23-item SSPDS showed excellent internal consistency (Cronbach's alpha between 0.70 and 0.89 for all health state scores, mean alpha was 0.79). Reproducibility for the total score (ICC=0.82) was high. ICC for single scores ranged from 0.42 for bodily discomfort to 0.88 for mobility. Concurrent validity for the total and individual SSPDS scores was good as reflected by high Pearson's r correlations with the PDQ-8 (r= 0.59 for cognitive functioning to r= 0.77 for the total score) and moderate to high correlations with the EQ-5D (r=-0.40 to r=-0.64). The ADR_NMS score was clearly separated from the other SSPDS scores, as shown by low correlations with the SSPDS health status scores (r=0.19 for emotional well-being to r=0.33 for mobility) and other measures (r=-0.14 for the EQ-5D VAS to r=-0.24 for the PDQ-8). CONCLUSIONS: The SSPDS is a valid and reliable PD-specific PRO measure to evaluate the severity of motor and non-motor symptoms. These symptoms load on the health status dimensions "bodily discomfort", "mobility", "cognitive functioning" and "emotional well-being". Additionally, it identifies symptoms that are caused or affected by adverse drug reactions (ADRs). It is short and easy to complete in daily routine.