Abstract Background: Endometrial carcinoma & benign entities like normal proliferative transformation, hyperplasia, & polyps can all lead to abnormal uterine cavity. Addition of three-dimensional (3D) sonohysterography to conventional sono-hysterography improves accuracy of endometrial pathology diagnosis. Three-Dimensional Saline Infusion Sono-Hysterography (3D SIS) assess uterine contour, adhesions, & focal pathologies with confidence. Aim of Study: To compare between accuracy of three-dimensional saline infusion sono-hysterography versus diag-nostic hysteroscopy in diagnosis of uterine cavity lesions. Patients and Methods: This was a prospective cohort research, conducted at Al-Hussein Hospital of Al-Azhar University on a total of 60 cases with uterine cavity lesions from March 2021 till March 2022. Results: 3D SIS was significant in detecting uterine cavity abnormality with sensitivity of 92.5% and specificity of 95% while PPV was 97% and NPV was 86% with accuracy of 93.3 %. Conclusion: Saline infusion sonohysterography in three dimensions is safe alternative to hysteroscopy. In diagnosis of uterine cavity lesions, it is comparable to hysteroscopy, & it may be used as primary technique for assessing uterine cavity when intracavitary lesions are suspected. Hysteroscopy is still gold standard for evaluating uterine cavity.