The objective of this multicenter observational study "Optimization levodopa therapy for patients with Parkinson's disease" (OPTIMA) was to evaluate the current practice of prescribing levodopa to patients with Parkinson's disease (PD) by general practitioners and specialists in the treatment of extrapyramidal disorders in Russia. The study included 763 patients with PD, stages from I to V according to Hoehn and Yahr staging of PD. Patients were randomized into three groups. Group I included 230 patients not previously treated with levodopa who needed treatment with this drug due to the motor deficit progression. Group 2 consisted of 262 patients treated with levodopa/carbidopa (nakom) who needed higher doses or the dose redistribution. Group 3 included 271 patients treated earlier with other levodopa preparations and currently needed treatment with levodopa/carbidopa (nakom). Primary symptoms of parkinsonism, motor deficit (motor fluctuations, dyskinesia) and non-motor symptoms (depression) were reduced after the beginning of treatment as well as after the increase in doses. The results revealed that the addition of levodopa/carbidopa can improve daily activities with the low risk of side-effects.