An 8-year old boy presented with a right neck swelling which appeared only intermittently. The swelling was well demonstrated by the Valsalva manoeuvre. The differential diagnosis include a laryngocele, a superior mediastinum tumour or cyst and a venous aneurysm. Plain radiography, computerized tomography, ultrasonography and venography were performed. A diagnosis of venous aneurysm was confirmed. Ultrasonography was the best modality for imaging of this rare condition. It is non-invasive and it will also delineate the extent of the lesion. The treatment is expectant. Surgery is reserved for cosmesis and symptomatic aneurysms.