Tumour localisation in Cushings disease (CD) can be challenging; most are microadenomas and 50% are <5 mm in diameter. They are, therefore, often difficult to detect by conventional MRI. Volumetric MRI (3D-SGE, spoiled-gradient echo 3D sequence) is a high spatial resolution scanning technique which uses very thin slices (1 mm). Theoretically, this increases the probability of finding small pituitary lesions when compared to conventional (spin-echo, SE) MRI techniques. We compared these MRI techniques in corticotroph microadenoma localisation. Twenty consecutive patients with biochemically confirmed CD underwent both conventional and volumetric MRI techniques. We excluded four patients with pituitary macroadenomas as the imaging in these patients is rarely problematic. Two patients are awaiting surgery. In the remainder, an experienced neuroradiologist (JE) classified conventional and volumetric scans as: definite lesion; equivocal lesion; normal gland. The analysis showed: In four patients, volumetric scanning revealed a lesion within a pituitary gland previously reported as normal on conventional MRI sequences. All four lesions were subsequently shown to be an ACTH-staining adenoma. In four patients, volumetric scanning was negative, with conventional imaging showing either a definite or equivocal lesion, each of which was subsequently histologically confirmed. In the other patients, volumetric scanning provided equivalent/complementary information to conventional imaging and/or the findings were equivocal and/or did not correlate with surgical findings. In the operated microadenoma patients, the remission rate was 86% (12/14). In both non-remission cases, no lesion was seen with either MRI sequence. Volumetric MRI may provide useful additional information to conventional MRI sequences to assist in surgical planning, but does not replace conventional sequences.