Background <p>Choroid plexus (CP) enlargement is found in Alzheimer’s disease (AD), multiple sclerosis, and Parkinson’s disease. As a source of cerebrospinal fluid (CSF), the diagnostic value of CP enlargement in idiopathic normal pressure hydrocephalus (iNPH) is unknown.</p> Purpose <p>This study aimed to evaluate the diagnostic performance of CP and CSF space volumes in iNPH.</p> Methods <p>We retrospectively collected patients with iNPH admitted to West china Hospital of Sichuan University (Chengdu, China) between June 2016 and December 2022 and patients with AD and healthy controls (HCs) from the ADNI database. CP and CSF space volumes were evaluated on magnetization prepared rapid gradient-echo (MPRAGE) MRI. We compared them among iNPH, AD, and HC group, and caluculated the area under receiver operating characteristic curves (AUC).</p> Results <p>A total of 32 patients with iNPH (mean age: 75 ± 5.7; 23 males), 32 patients with AD (mean age: 75 ± 4.3; 23 males), and 32 HCs (mean age: 75 ± 2.4; 23 males) were included. The CP volume in the iNPH group (1769 ± 486 mm³) was larger than that in the AD group (1116 ± 329 mm³; p &lt; .001) and the HC group (798 ± 307 mm³; p &lt; .001). The largest AUC were achieved for CP volume (0.92; 95% CI 0.86–0.97) and lateral ventricle volume (0.92; 95% CI 0.86–0.98).</p> Conclusions <p>CP volume showed good performance in distinguishing iNPH from non-iNPH patients (AD and HC). CP volume may be a good imaging indicator in the diagnosis of iNPH.</p>