<p>Parkinson’s disease (PD) is one of the commonest neurodegenerative diseases, second only to Alzheimer’s disease. PD is characterized by the involvement of multiple systems and a steady progression of the pathological process, leading inevitably to the development of variety of symptoms. The symptoms of PD are divided into motor and non-motor symptoms. It is generally accepted that non-motor symptoms precede motor symptoms and appear several decades before motor symptoms. The most common non-motor symptom of PD is depression, which significantly reduces patients’ quality of life. This review examines the latest research into the pathophysiology of depression in PD. The analysis revealed the involvement of the substantia nigra, pontine raphe nuclei, and locus ceruleus in the development of depression in PD. The molecular basis for the dysfunction of these areas is deficit of dopamine, serotonin, and noradrenaline. Detailed study of the neurobiological mechanisms of the occurrence and progression of depression will enable effective and pathogenetically sound therapeutic approaches to be developed.</p>