Abstract: Objective To assess the diagnostic performance and inter-observer agreement of the Ovarian-Adnexal Reporting and Data System ultrasound （O-RADS） combined with contrast-enhanced ultrasound （CEUS）. Methods Clinicopathological data of 123 adnexal lesions from 123 patients admitted to the University of Hong Kong-Shenzhen Hospital and the Seventh Affiliated Hospital of Sun Yat-sen University from July 2021 to December 2023 were collected. Each lesion was subject to CEUS before surgery. Each lesion was assigned to an O-RADS US category with histopathological results as the gold standard. The CEUS features of each lesion were recorded and used to calculate the total CEUS scores. Lesions were then re-rated according to O-RADS plus CEUS scores. Kappa （κ） statistics were applied to assess inter-observer agreement between a less experienced and an expert radiologist. Results Of the 123 adnexal lesions, 94 were benign and 29 were malignant. The malignancy rates of O-RADS 5, O-RADS 4 and O-RADS 3 lesions were 81.25%, 20.83% and 2.86%, respectively. The malignancy rates of O-RADS+CEUS 5, O-RADS+CEUS 4, O-RADS+CEUS 3 and O-RADS+CEUS 2 lesions were 75%, 21.74%, 0% and 0%, respectively. The area under the receiver operating characteristic （ROC） curve （AUC） of two observers were 0.791 （95% CI 0.891-0.976） and 0.934 （95% CI 0.697-0.886）, respectively. The diagnostic performance of O-RADS plus CEUS was higher than that of O-RADS alone （P = 0.0004）. Taking ≥ O-RADS 4 as the cut-off value for malignant lesions, the sensitivity and specificity of O-RADS and O-RADS+CEUS were 0.966 （95% CI, 0.822-0.999） and 0.362 （95% CI 0.265-0.467）, 1.000 （95% CI 0.881-1.000） and 0.723 （95% CI 0.622-0.811）, respectively. The inter-observer agreement between a less experienced and an expert radiologist of O-RADS and CEUS features were good or very good （κ 0.668-0.840）. Conclusions Compared with O-RADS, O-RADS plus CEUS shows better diagnostic specificity for malignant adnexal lesions. The inter-observer agreement between a less experienced and an expert radiologist of O-RADS and CEUS features is good.