**1. Introduction**

Adrenal gland tumors are common entities in clinical practice. They are divided as functioning (which produces hormones) and the nonfunctioning ones (also known as silent). In terms of their biological behavior, they may be divided in benign or malignant tumors. The term "incidentaloma" refers to adrenal masses that are found in image exams aiming at investigating disturbances unrelated to the adrenal glands [1–3].

Most adrenocortical tumors are benign, unilateral, nonfunctioning adenomas with less than 4 cm in diameter that are found during abdominal image studies [3]. The functioning adrenal tumors are generally the benign adenoma type, which

cause, for instance, the Cushing's syndrome, primary aldosteronism, or, not so commonly, virilization [1, 2].

This present chapter discusses the preoperative assessment of patients suffering from this condition. It mainly focuses on:

