A study included 68 patients with parkinsonism: 43 of them were treated with proflusak (fluoxetin), which efficacy was assessed in the frames of randomized placebo-controlled study. The levels of motor disability, anxiety, depression and serum serotonin (S) concentration were measured. The prevalence of rigidity and hypokinesia caused the increase of the depression level, along with decreasing of S concentration. Severity of tremor was positively correlated with the level of anxiety and blood S. Significant differences between patients receiving proflusak and placebo were found. No changes in the levels of motor-affective symptoms were observed in the placebo group. In patients treated with proflusak, the subjective improvement of health was accompanied by the significant decrease of depression severity and reduction of movement deficit, in particular rigidity and hypokinesia. The blood concentration of S decreased significantly in comparison to the placebo group. Taking into account the mechanism of action of the drug studied (its belonging to SSRIs), these changes may reflect the alterations of serotonergic metabolism in the brain synapses.