Autosomal dominant polycystic kidney disease (ADPKD) is a systemic disorder well known for its association with intracranial aneurysms. A series of patients with ADPKD who were screened for the presence of an intracranial aneurysm were reviewed and found to include an unexpectedly high number with intracranial arachnoid cysts. Among 247 patients with ADPKD who underwent magnetic resonance imaging (180 cases) or high-resolution contrast-enhanced computerized tomography (67 cases), there were 151 women and 96 men with a mean age of 44 years. Intracranial arachnoid cysts were found in 20 patients (8.1%) with ADPKD compared to two (0.8%) in a control group without ADPKD matched for age, sex, and method of imaging (p < 0.0001). Multiple intracranial arachnoid cysts were found in two patients. Polycystic liver disease was present in 17 (85.0%) of the 20 patients with intracranial arachnoid cysts compared to 119 (52.4%) of the 227 patients without (p < 0.004). Pineal cysts were found in two patients (0.8%) and choroid plexus cysts were found in three patients (1.2%) but this was not different from the control population. None of the intracranial cysts was symptomatic and none was treated surgically. Intracranial arachnoid cysts are a relatively frequent incidental finding in patients with ADPKD, providing further support for the systemic nature of this disease. In the authors' experience with approximately 1500 patients with ADPKD, no complication has been encountered from an intracranial arachnoid cyst, suggesting that asymptomatic intracranial arachnoid cysts in patients with ADPKD require no treatment.