Most cases of Parkinson's disease (PD) are idiopathic, but some characteristics, such as early onset or a positive family history, raise suspicions of an inherited form of the disease. In the last decades several genes have been linked to parkinsonism, with different patterns of inheritance and different clinical phenotypes. Positron emission tomography (PET) imaging has helped to characterize genetic-linked parkinsonism, thanks to the availability of dopaminergic and nondopaminergic tracers. On the other hand, investigation of molecular changes in mutation carriers, even at preclinical stages, has provided a deeper comprehension of the pathogenesis of PD and of the compensatory mechanisms that take place in the very early stages of the disease.