The aim of this study was to evaluate the sensitivity and accuracy of computed tomography (CT) scanning, 75Se-selenomethyl-norcholesterol scintigraphy (SNS) and magnetic resonance imaging (MRI) in patients with Cushing's syndrome (CS) undergoing adrenalectomy. A series of 67 patients with CS due to benign adrenal disease was reviewed. There were 11 (16.4%) men and 56 (83.6%) women, with an overall median age of 44 years (range 19-69 years). Prior to surgery all patients underwent both CT and SNS, and 58 (86.6%) underwent adrenal MRI. Thirty-five (52.2%) of the patients (group A) had histologically confirmed unilateral adrenal involvement (33 patients with a solitary adrenocortical adenoma, and two with unilateral nodular cortical hyperplasia), while 32 (47.8%) of the patients (group B) had CS caused by bilateral adrenal involvement, including two patients with multinodular adrenal hyperplasia. The sensitivity, specificity and accuracy of adrenal imaging in group A were 97.1%, 100% and 98.5% for SNS, 94.3%, 68.7% (P<0.05, chi2 test) and 82.1% for CT scan, and 92.3%, 60.0% (P<0.05) and 64.3% (P<0.05) for MRI, respectively. In group B the sensitivity, specificity and accuracy were 100%, 97.2% and 98.5% for SNS, 64.5% (P<0.05), 97.2% and 82.1% for CT scan, and 60.0% (P<0.05), 92.3% and 35.7% (P<0.05) for MRI, respectively. In conclusion, SNS represents the most sensitive and specific adrenal imaging study and should be used in all patients with confirmed biochemical diagnosis of CS undergoing adrenalectomy. The sensitivity and specificity of CT scan and MRI are similar, but the latter shows a lower accuracy, especially in patients with bilateral adrenal involvement.