Two cases of delayed non-mycotic false aneurysm arising from ascending aortic cannulation site, presenting one-and-a-hald years and seven years after cardiopulmonary bypass, are described. These two cases represent an incidence of 0.12% of this complication. Repair using profound hypothermia and circulatory arrest with femoral artery and femoral vein cannulation for cardiopulmonary bypass is recommended. The advantages and complications of aortic cannulation are discussed and recommendations to minimise the complications of cannulation are made. The clinical presentation and diagnosis of non-mycotic false aneurysms arising from the aortic cannulation site are described. In addition one delayed and two early cases of non-mycotic cannulation site false aneurysms previously published are analysed. Surgeons should be alert to the possibility of this complication in all patients who have had aortic cannulation for cardiopulmonary bypass even in the distant past. Unexpected symptoms such as constant anterior chest pain, dysphagia, hoarseness, and increasing widening of the superior mediastinum on the chest radiograph warrant prompt investigation.