To evaluate observer performance in adrenal scintigraphy with two different imaging instruments and to assess the requirement for computer processing in routine adrenal imaging, gamma-camera images (analog and computer processed) and Anger tomoscanner studies were independently interpreted by three observers. Thirty-eight pairs of images were used for the analysis of the receiver operating characteristic (ROC) curve in comparing the tomoscanner with the large-field gamma camera, and 44 pairs of images were used for the comparison of the gamma camera analog images with computer-processed images. ROC analysis demonstrated a higher detection rate for the tomographic images. The computer-processed images did not improve adrenal detection. When each case was considered individually, the tomoiscanner was preferred in 37% of cases, and in 50% of cases, both instruments were considered to be equaly valuable.