Objective: To evaluate the function of serum dehydroepiandrosterone sulfate (DHEAS) in adult adrenal space-occupying lesions. Methods: In this cross-sectional study, 395 patients with adrenal space-occupying lesions who had their DHEAS levels measured were collected from the First Medical Center of Chinese PLA General Hospital from January 2010 to June 2021. They were divided into the adrenal Cushing syndrome (ACS) group (n=100) and non-ACS group (n=295). The former was divided into the cortisol-producing adrenal adenoma (CPA) group (n=67) and primary bilateral macronodular adrenal hyperplasia (PBMAH) group (n=33). Clinical data of each group were collected and compared among groups by independent samples t-test, chi-square test, and Mann-Whitney U test. Serum DHEAS ratio corrected for age and sex was further constructed to identify the receiver operating characteristic curve and the optimal tangent point value for different adrenal occupation. Results: Patients in the ACS group were younger (44.9±13.7 vs. 49.9±12.5, P=0.001); had a larger proportion of women (79/100 vs.139/295, P=0.001); and had higher cortisol levels [8∶00Am, 497.31 (343.52, 606.50) vs. 353.11 (267.50, 487.91) nmol/L, P<0.001] than those in the non-ACS group. The serum DHEAS level and ratio in the ACS group were significantly lower than those in the non-ACS group [0.50 (0.40, 1.21) vs. 2.68 (1.56, 4.32) μmol/L, 1.00 (0.43, 1.68) vs. 3.17 (2.21, 4.54), both P<0.001]. When the serum DHEAS ratio cut-off point was 1.29, the sensitivity and specificity for differential diagnosis of ACS and non-ACS were 72.0% and 91.5% respectively. The ratio of DHEAS in the CPA group was lower [0.58 (0.27, 1.05) vs. 1.14 (1.04, 2.40), P<0.001] than that in the PBMAH group. When the serum DHEAS ratio cut-off point was 0.99, the sensitivity and specificity for differential diagnosis of CPA and PBMAH were 64.2% and 81.2% respectively. Conclusion: Corrected age-sex DHEAS ratio can assist in the functional assessment of adrenal space-occupying lesions.