Differentiating between infundibular dilatations and aneurysms might be challenging even with to-date modalities. While infundibular dilatation has been regarded as an incidental “leave alone” lesion, a more extended intervention might be needed for an aneurysm. This study presented a 23-year-old woman with an infundibular dilatation at an unusual site at the A1 segment of the anterior cerebral artery from 3D digital subtraction angiography, initially identified as an aneurysm on magnetic resonance imaging and computed tomography angiography. Points in differentiating infundibular dilatation and aneurysm are thoroughly elaborated in the discussion. © 2024, EduRad. All rights reserved.