Neurodegenerative diseases are characterised by progressive neuronal loss due to the accumulation of misfolded proteins into the brain, underpinned by complex geneenvironment interactions. Among them, Parkinson's disease (PD) and other related conditions are defined by slowness of movement, tremor and rigidity, i.e. parkinsonism. This is caused by a progressive degeneration of dopaminergic neurons and impaired function of the basal ganglia. While diagnostic criteria are mainly based on clinical appraisal and definite diagnosis relies on post-mortem evaluation, structural and functional brain imaging allows to assess the intricate pathophysiological processes underlying neurodegeneration in vivo. Notably, positron emission tomography (PET) and single photon emission computed tomography (SPECT) imaging can estimate the pathogenic pathways involved in degenerative parkinsonisms. This includes impaired density of neurotransmitters receptors and transporters (e.g. dopamine and serotonin), altered brain metabolism, abnormal protein aggregation as well as neuroinflammation, all of which can be detected in early forms or even before the onset of motor symptoms in high-risk populations. My line of research aims at improving the diagnostic performance of degenerative parkinsonisms, notably by using PET/SPECT in addition to structural brain imaging. Moreover, my objectives include to better understand the pathophysiological role of tau deposition and brain inflammation in these conditions. Neurodegenerative diseases lead to motor, cognitive and emotional disability, and have a major impact on patients' quality of life. They also place a tremendous burden on families, caregivers, and society. Although dopamine-replacement therapy and deep brain stimulation are valid therapeutic options, they are symptomatic and thus do not halt disease progression. In combination with clinical and other biological markers, molecular imaging will certainly contribute to gain further insight into the complex pathophysiological mechanisms involved in neurodegeneration and to help developing disease-modifying treatments.