The perivascular spaces (PVSs) are pia-lined potential spaces filled with interstitial fluid (ISF) and form a network throughout the brain, which is a part of glymphatic system and helps to derange of metabolites from cerebral parenchyma. The enlarged PVSs are the most common cystic lesion of the brain and gradually become prominent with age. Literally, tumefactive PVS is the giant enlargement of PVS, measuring 15 mm and more in size, and thought to be result of blocking of the outlet of ISF for any reason. Typically, they tend to from clusters of cysts, but tumefactive forms are usually solitary. They usually have moderate mass effect and can cause obstructive hydrocephalus when located in mesencephalothalamic region. Although they don’t contain cerebrospinal fluid (CSF), they have similar signal to CSF on all magnetic resonance imaging (MRI) sequences and do not enhance. These MRI features are very useful for their differential diagnosis from other congenital, infectious, ischemic and tumoral cystic/necrotic lesions. The precise diagnosis of PVS is critical to prevent patients with “leave-me-alone” lesions, from unnecessary surgical interventions.