Abstract Disclosure: A. Kittithaworn: None. P. Dogra: None. L. Rahimi: None. R. Sandooja: None. I. Bancos: None. Background: Adrenal calcification is discovered incidentally on imaging performed for reasons other than adrenal pathology and represents <1% of benign adrenal lesions. Data on the etiology and morphology of adrenal calcifications are scarce. Objective: To determine the etiology and imaging characteristics of adrenal calcification. Methods: We conducted a single-center retrospective study of patients with adrenal calcification on abdominal computed tomography between January 1st,2017 and December 31st, 2021. Medical records were reviewed for demographics, discovery mode, etiology and morphology. Subgroup analysis of patients with calcification/s associated with an adrenal mass was performed. Results: Adrenal calcification was reported in 540 patients (245, 45% women, median age 65 years (IQR 54-74). Only a minority of patients with adrenal calcifications were evaluated by an endocrinologist (167, 31%). Adrenal calcifications were discovered incidentally in 472 (87%) patients, during cancer staging imaging in 66 (12%), and evaluation of other symptoms in 2 (<1%). The etiology of adrenal calcification was most commonly idiopathic (390, 72%), followed by adrenal mass (112, 21%), hemorrhage (20, 6%), and granulomatous disease (8, 1.5%). Adrenal calcifications were bilateral in 34 (6%) patients and unilateral in 506 (94%), with a similar left and right distribution. Unilateral calcifications were more frequently single (399, 79%) with punctate (60%), coarse (28%), linear/curvilinear (9%), or eggshell (3%) morphology. Bilateral adrenal calcifications presented more frequently with multiple lesions (53% vs 21% in unilateral calcifications, p <0.0001), and were coarse (59%), punctate (29%), or linear (9%). When associated with either unilateral or bilateral adrenal mass, calcifications were either central (50, 45%), peripheral (44, 39%), septal (10, 9%), or both central and peripheral (7, 7%) in relation to the adrenal mass. Adrenal masses associated with adrenal calcifications were: adrenal adenomas in 63 (56%), myelolipomas or cysts in 28 (23%), metastases in 12 (11%), adrenal carcinomas in 4 (4%), pheochromocytomas in 2 (2%), and other rare masses in 3 (3%) patients. Patients with adrenal calcifications associated with an adrenal mass were younger at the time of diagnosis (median of 63 vs 66 years, p=0.014), and had a higher proportion of women (61% vs. 41%, p=0.0002), and were more likely to be discovered during cancer staging imaging (21% vs. 10%, p=0.003). Adrenal mass-associated calcifications were more frequently multiple rather than single lesions (46% vs. 17%, p<0.0001). Conclusion: Adrenal calcifications are usually unilateral single punctate or coarse lesions of unclear etiology. The majority of the adrenal masses that demonstrated calcifications were benign, however adrenal malignancy or pheochromocytomas were diagnosed in 17% of cases. Presentation: Friday, June 16, 2023