Introduction: Hypercortisolism requires a prompt therapeutic management to reduce the risk of development of a potential fatal emergency. A synchronous bilateral adrenalectomy (SBA) is effective in recovering hypercortisolism. However, specific indications for an SBA are not available. We aimed to evaluate the outcome of patients who underwent an SBA and to identify biomarkers able to predict the requirements of an SBA. Patients and methods: A mono-centric and longitudinal study was conducted on 19 consecutive patients who underwent SBA for ACTH-dependent hypercortisolism between December 2003 and December 2017. This study population was compared to two control groups composed of patients cured after the resection of the ACTH secreting pituitary adenoma (Group A: 44 patients) and of the ACTH-secreting neuroendocrine tumours (Group B: 8 patients). Results: Short- or long-term SBA complications or the recurrence of hypercortisolism did not occur. A single patient experienced Nelson syndrome. Clinical features after SBA showed improvement in the glico-metabolic assessment, hypertension, bone metabolism and the occurrence of hypokalaemia and infections. The younger the age at the time of Cushing's disease diagnosis, the longer the duration of active hypercortisolism, higher values of plasmatic ACTH and Cortisol (1 month after pituitary neurosurgery) and higher values of Ki67 in pituitary adenomas were detected in this study population as compared to Group A. Conclusions: SBA is an effective and safe treatment for patients with unmanageable ACTH-dependent hypercortisolism. A multidisciplinary team in a referral centre with a high volume of patients is strongly recommended for the management of these patients and the identification of patients, for better surgical timing.