The aim of this work was to test remaining adrenal tissue after subtotal adrenalectomy (STAE) with respect to its post-surgical dimensional and functional dynamics. The patients collective cosisted of a total of 11 patients analysed, which comprised 6 unilateral and 5 bilateral surgeries for 8 pheochromocytomas, 1 Conn syndrome, 1adenoma and 1 bilateral adrenal hyperplasia. The sizes of post-interventional adrenal remnants were measured at three time points, namely intraoperatively through the surgeon, as well as by computed tomography (CT) within the first 5 days and three months thereafter. Additionally, at both of these post-operative points, adrenal stress competence was tested using conventional ACTH-tests. We found that the size of the adrenal remnants could not be measured exactly during surgery, especially if they were smaller than 5 mm. Both adrenal glands gained in size within the course of 3 months in patients who underwent bilateral surgery, which was confined to the contralateral adrenal remnants only in patients with unilaterally intervention. In the two patients in which the adrenal remnants showed a volume of less then 3.5 ml, a permanent reduction of adrenal function according to negative test results was demonstrated. We conclude that in order to preserve adrenocortical function - following subtotal adrenalectomy-, but without compromising the onco-surgical objective, it is necessary to maintain as much adrenal tissue as possible. Thereby, surgeons should be aware of the more reliable determination of actual adrenal tissue residues through CT-based methods in the post-operative phase.