REal-life ON PARKinson's - ITaly (REONPARK-IT)

Inclusion Criteria: 1. The patient is able to comprehend and willing to provide written informed consent to participate in this study. 2. Patients aged 30 years or older. 3. The patient has a clinical diagnosis of PD according to the diagnostic criteria of United Kingdom (UK) PD Society Brain Bank (2006) or Movement Disorder Society (MDS) Clinical Criteria (2015). 4. Disease severity stages I-III (Hoehn \& Yahr Staging). 5. The patient is on treatment with levodopa/DOPA decarboxylase inhibitors (DDCI) for at least 1 year. 6. The patient has signs of wearing off phenomenon/end-of dose motor fluctuations for less than 2 years. 7. Patients starting treatment with opicapone as per local Summary of Product Characteristics (SmPC). Initiation of treatment with opicapone will be independent from participation in this observational study and must not be initiated for the purpose of study participation. The decision to treat patients with opicapone will occur before patients are enrolled in the study. Exclusion Criteria: 1. The patient has any form of Parkinsonism other than PD. 2. The patient is participating in a clinical trial with an investigational drug or has concluded participation within 30 days. 3. The patient has any contraindication to opicapone according to SmPC. 4. The patient meets criteria for dementia in the Investigator's judgment. 5. The patient is currently treated with catechol-O-methyl transferase (COMT) inhibitors.