Transcranial sonography (TCS) allows high resolution imaging of deep brain structures, provided sufficient imaging conditions and adequate qualification of the investigator. Since TCS can display changes of midbrain structures and basal ganglia that are not or only heavily detected with other neuroimaging methods, TCS has yielded new insights into the pathogenesis also of non-motor features of PD. Abnormal increased echogenicity ('hyperechogenicity') of substantia nigra is not only a characteristic finding in PD, but is also related to increased risk of depression in PD patients (relative risk [RR], 1.9). Reduced echogenicity ('hypoechogenicity') of midbrain raphe indicated increased risk of depression (RR, 2.0) and urinary incontinence (RR, 4.7) in PD patients. Caudate nucleus hyperechogenicity was associated with drug-induced psychosis (RR, 2.4), and frontal-horn dilatation >20mm with dementia (RR, 3.6). TCS findings support the hypothesis of a pathogenetic link between depression and PD. Further studies are warranted to find out whether TCS is useful for detecting increased risk for non-motor complications, such as depression, psychosis, or urinary incontinence, already before they become clinically obvious.