The comorbidity in Parkinson’s disease (PD), which is closely related to the tolerability of antiparkinsonian drugs, is analyzed. The authors present the results of the studies that have confirmed the greater safety of rasagiline compared to dopamine receptor agonists in elderly patients. The effects of rasagiline, including combinations of this drug with antidepressants, on depression in PD and the low risk of the serotonin syndrome caused by these combinations are considered. The studies demonstrated the effect of rasagiline on fatigue and cognitive functions in PD patients are described. Single cases of the development of impulsive-compulsive disorders in patients treated with rasagiline are presented.