Whether 360 degrees or 180 degrees imaging should be used in cardiac thallium-201 single-photon emission tomography (SPET) studies to detect coronary artery disease remains controversial. Moreover, the relative diagnostic accuracy of 360 degrees and 180 degrees 201Tl SPET for the assessment of myocardial viability has never previously been studied. The aim of this study was to perform a direct comparison between 180 degrees and 360 degrees data sampling to detect viable myocardium in patients undergoing revascularization; in order to allow optimal detection of viability a rest-redistribution protocol was used. The 201Tl results were compared with improvement of regional wall motion abnormalities after the revascularization, which was considered as the "gold standard" for myocardial viability. Thirty-two patients, scheduled for revascularization, underwent rest-redistribution 201Tl SPET, using a 360 degrees arc. Raw data along a 180 degrees arc (45 degrees RAO to LPO) were selected from the original 360 degrees data sets (both early an late 201Tl images). All SPET data were analysed semiquantitatively using circumferential profiles of the short-axis images; the data were displayed in polar maps. Criteria for viability included percentage 201Tl redistribution and percentage 201Tl activity on the late image. Regional wall motion was assessed with two-dimensional echocardiography before and 3 months after revascularization. The sensitivities of 360 degrees and 180 degrees imaging for the prediction of functional recovery were 82% and 89%, respectively, whereas the specificities were 51% and 55%, respectively. The diagnostic accuracy of 360 degrees imaging was 62% and that of 180 degrees imaging 67%. This study shows that 360 degrees and 180 degrees imaging have comparable diagnostic accuracy in the prediction of functional recovery after revascularization. With the newer dual-head gamma camera systems with each detector opposing each other, 360 degrees imaging may be preferred.