Comparing Different Levodopa/Carbidopa/Entacapone Treatment Regimens

Inclusion Criteria: * Written informed consent (IC) obtained. * Male or female patients with idiopathic PD according to the United Kingdom brain bank criteria with end-of-dose motor fluctuations * Hoehn and Yahr stage 2-4 performed during the "ON" state. * Duration of response between 1.5 and 4 hours (based on medical history) to the patient's first morning dose of levodopa/dopa decarboxylase inhibitor (DDCI) with or without entacapone. * Treatment with 3-8 daily doses of levodopa/DDCI with or without entacapone with a total daily levodopa dose in the range of 300-1200 mg. One evening dose of controlled-release formulation of levodopa/DDCI is allowed provided that it is included in the total of 3-8 daily doses of levodopa/DDCI mentioned above. * Unchanged levodopa/DDCI with or without entacapone and other antiparkinsonian medication(dopamine agonists, monoamine oxidase \[MAO\] B inhibitor, amantadine and/or anticholinergics with approved doses), if any, for at least 6 weeks prior to the screening visit. * Age of 30 years or above Exclusion Criteria: * Secondary or atypical parkinsonism. * Use of tolcapone within 6 weeks prior to the first treatment period. * Previous tolerability problems with entacapone or tolcapone. * Concomitant treatment with apomorphine, MAO-A inhibitors or nonselective MAO inhibitors. * Concomitant treatment with drugs having antidopaminergic action including alpha-methyldopa, reserpine and antipsychotic drugs (also D2 receptor blocking antiemetics except domperidone). As an exception, an evening dose of an atypical antipsychotic is allowed. * Use of any iron preparations. * Intensity of dyskinesias which would, in the opinion of the investigator, interfere with the interpretation of motor part (part III of the Unified Parkinson's Disease Rating Scale (UPDRS III) scoring during the levodopa challenge test. * Currently active hallucinations. * Severe orthostatic hypotension as judged by the investigator. * Mini-Mental State Examination (MMSE) score \< 26 * History of neuroleptic malignant syndrome (NMS) and/or non-traumatic rhabdomyolysis. * Past or current treatment with deep brain stimulation (DBS) or other surgical treatment for PD. * Treatment with levodopa or dopamine agonist infusion or injection * Active malignancy, narrow-angle glaucoma or pheochromocytoma. * Clinically significant cardiovascular, pulmonary, gastrointestinal, hepatic, renal, neurological or psychiatric disorder or any other major concurrent illness that in the opinion of the investigator would interfere with the interpretation of the study results or constitute a health risk for the subject if he/she takes part into the study. * Alanine aminotransferase or aspartate aminotransferase \> upper limit of normal at screening. * Any other abnormal value of laboratory, vital signs or electrocardiogra (ECG) which would in the opinion of the investigator interfere with the interpretation of the study results or cause health risk for the subject if he/she takes part into the study. * Female patients of childbearing potential (i.e. menstruating or less than 2 years postmenopausal) if they are not using proper contraception (hormonal contraception, intrauterine device \[IUD\] or surgical sterilisation, spermicidal foam in conjunction with condom on male partner). * Patients with pre-planned elective surgery. * Known hypersensitivity to active substances or to any of the excipients of the study drugs. * Participation in a drug study within 60 days prior to entry to this study. * Any other condition that in the opinion of the investigator would interfere with the interpretation of the study results or constitute a health risk for the subject if he/she takes part into the study.