To compare the results of transthoracic contrast echocardiography (TTCE) adding a grading scale with the results of thoracic computed tomography (CT) in order to optimise the use of both techniques. 95 patients with hereditary haemorrhagic telangiectasia (HHT) were examined with TTCE and thoracic CT to detect pulmonary arteriovenous malformations (PAVMs). According to previous studies, TTCE was divided into a four grade scale depending on the degree of opacification of the left ventricle after the administration of a contrast agent. Of the 95 patients (50.5% female; mean age 46 yrs), none with normal or grade 1 TTCE had detectable PAVMs on thoracic CT. Shunts of grades 2, 3 and 4 were associated with PAVMs according to thoracic CT in 25, 80, and 100% of the cases. There was a statistically significant association between the TTCE grade and the detection of a PAVM by thoracic CT. There were also statistically significant associations between TTCE grade and the cardiac cycle when the contrast was first visible in the left atrium, and size of the feeding artery. Graded TTCE and timing of left atrium opacification may be useful techniques in selecting HHT patients for PAVM screening with thoracic CT scans.