We report a case of a 21-year-old man with a popliteal venous aneurysm of the left popliteal fossa, with local symptoms and pain during palpation. Early diagnosis is fundamental in order to prevent the thromboembolic events or other major complications. Duplex scanning, Computed Tomography scanning, and Magnetic Resonance imaging are considered to be important non-invasive diagnostic methods for the diagnosis of PVA. The Angio Computed Tomography acquisition confirmed a 36 mm x 17 mm oval mass in the left popliteal fossa continuous with the popliteal veins. This lesion had presented contrast enhancement only in delayed acquisition (180 sec) and so appeared to be a true venous aneurysm and no arterial. The PVA was repaired surgically via a posterior approach to the popliteal fossa. A 4 x 2 aneurysm was identified. In the same time open tangential aneurysmectomy and lateral vein reconstruction were realised. This case is interesting because the Angio Computed Tomography study, in delayed acquisition, has allowed a correct diagnostic assessment of PVA and the surgical treatment.