The aim of the present study was to compare between the accuracy of 2D sonohysterography and 3D in determine the myometrium thickness at the level of the isthmus uteri & location of scar defect in women with previous cesarean section. A total of 33 women with previous cesarean section at least 3 months post cesarean section before they were enrolled in the study. For all participants; 2D and 3D sonohysterography were performed. Results obtained by 3D ultrasound were significantly higher than results obtained by 2D ultrasound. Mean thickness of myometrium was 0.63 cm as obtained by 3D ultrasound while it was 0.48 by 2D ultrasound (p-value < 0.05)We found that 3D ultrasound readings were significantly correlated with both age and number of previous CS (negative correlation) while 2D reading were significantly correlated with only number of previous CS. There was statistically significant positive correlation between readings of 2D and 3D ultrasound.In conclusion, the present study found that 3D ultrasound is as accurate as 2D ultrasound in evaluating scar thickness and detection of scar defect. Experience and learning curves are very essential in determining the accuracy of such procedure.