Incidentally detected adrenal masses are increasingly encountered in clinical practice due to better availability and accessibility of imaging procedures and are considered to be amongst the most common tumors in humans, with an estimated prevalence ranging from 0.4 to 4.4%. Malignancy is rare amongst patients with adrenal incidentalomas presenting in an endocrine clinic. The imaging phenotype is very helpful in distinguishing benign adenomas from malignant lesions. From the endocrine standpoint, catecholamine and aldosterone producing tumors are infrequent but subtle abnormalities of cortisol secretion are commonly encountered. Subtle autonomous glucocorticoid hypersecretion has a reported prevalence that varies from 1 to 47%, according to the applied diagnostic criteria. Currently there is no consensus on the definition of subclinical hypercortisolism. Nevertheless the dexamethasone suppression tests seem to better accomplish the task of unmasking subtle abnormalities of cortisol secretion. Although the clinical implications of subclinical hypercortisolism remain elusive, it has been associated with the occurrence of various metabolic abnormalities, such as diabetes, hypertension, obesity and dyslipidemia. Moreover, impaired bone mass density and even a higher fracture rate have been reported. Although incidentally discovered adrenal masses are most commonly unilateral, a substantial proportion of patients, ranging from 8.9 to 17% of cases, are presenting with bilateral lesions. In these patients the prevalence of subclinical hypercortisolism is much higher compared to those presenting with unilateral lesions. Involvement of aberrant receptors as shown by the demonstration of paradoxical responses to meal, posture or LHRH has been detected in few patients with bilateral incidentalomas. Surgical intervention in selected cases results in some beneficial effects but more data are required in order to routinely support surgery in this clinical setting.