Purpose To explore the diagnostic efficiency of ultrasound(US)combined with contrast-enhanced ultrasound(CEUS)in breast lesions and to analyze the related factors affecting the diagnostic accuracy.Materials and Methods From January 2022 to February 2023,the clinical data and ultrasound images of 784 patients who underwent breast US and CEUS examination with definite pathological results were retrospectively collected in the First Medical Center of the PLA General Hospital.The diagnostic efficacy of US combined with CEUS in benign and malignant breast lesions was analyzed,respectively.The independent risk factors for diagnostic errors were analyzed via Logistic regression.Results The sensitivity,specificity and accuracy of US combined with CEUS in the diagnosis of benign and malignant breast lesions were 89.2%,84.4%and 88.7%,respectively.The area under the receiver operating characteristic curve was 0.932.The results of multivariate Logistic regression analysis showed that the diagnosis error rate increased when the lesions were non-mass type(odds ratio,OR=1.927,P=0.047),complex cystic and solid(OR=3.729,P=0.000),and high-enhanced CEUS(OR=1.937,P=0.023),while the diagnosis error rate decreased when the lesions were large(OR=0.688,P=0.004)and with US-detect suspicious lymph node(OR=0.143,P=0.011).Conclusion When the breast lesions are non-mass type,complex cystic and solid lesions and hyper-enhancement,the diagnosis error rate of US combined with CEUS increased.It is necessary to further explore the enhancement patterns of different lesions.