Hydrocephalus is a disease and cerebral atrophy is an imaging manifestation. Imaging examination to diagnose hydrocephalus needs to be differentiated from cerebral atrophy. 1. Hydrocephalus: Hydrocephalus refers to a pathological condition in which the secretion, circulation or absorption of cerebrospinal fluid is impaired, leading to an increase in intracranial cerebrospinal fluid and causing an abnormal enlargement of the ventricles and/or subarachnoid space. It is common in infants and young children due to congenital developmental problems, and in adults due to intracranial infections, traumatic brain injury, and cerebral hemorrhage. Imaging manifestations are ventricular dilatation, periventricular white matter interstitial edema, chronic hydrocephalus can also appear cortical thinning, atrophy. 2. Cerebral atrophy: Cerebral atrophy refers to the shrinkage of the volume of brain tissue structure caused by various reasons, the reduction of brain parenchyma, the reduction of brain mass, and the reduction of the number of brain cells. It can be seen in heredity, traumatic brain injury, cerebral infarction, encephalitis, cerebral ischemia, hypoxia, cerebral arteriosclerosis, gas poisoning, alcoholism. Imaging shows a series of changes such as flattening of the cerebral gyrus, widening and deepening of the sulci, and enlargement of the ventricles, cerebral pools, and subarachnoid space. Since all imaging shows ventricular dilatation and other manifestations, clinical diagnosis needs to be differentiated. In hydrocephalus, the ventricles dilate more uniformly, the anterior horns of the two lateral ventricles are balloon-shaped, the posterior legs of the lateral ventricles may be rounded and dilated, and the sulci become shallow or disappear. In atrophy, the anterior and posterior horns of the lateral ventricles tend to be pointed, while the sulci deepen. When the imaging results show abnormal manifestations, it is recommended to consult the clinician in time and not to diagnose by oneself to avoid delaying the condition.