Background: The assessment of the volume status in critically ill paediatric patients in intensive care units is vitally important for fluid therapy management. The most commonly used parameter for detecting volume status is still central venous pressure (CVP). However, in recent years, various kinds of methods and devices are being used for volume assessment in intensive care units to minimize the many complications of invasive central venous catheter insertion. Objective: This study aimed to use internal jugular vein (IJV) or inferior vena cava collapsibility indices (CI) by ultrasonography as a first-line approach for the bedside non-invasive assessment of central venous pressure/fluid status in critical ill intensive care unit patients. Patients and Methods: This study was carried out on 67 patients of both sex who were admitted to the Surgical Intensive Care Units of Anesthesia Department, Faculty of Medicine, Zagazig University Hospitals during the period from January 2021 to January 2022. Results: There were a statistical significance decrease in all CI among cases had CVP >10 mmHg compared to cases had CVP ≤10. CI of IJV at 0 degree at cut off >21.4 had sensitivity 88.4%, specificity 79.2% and accuracy 85.1% in prediction of CVP ≤ 10 while at 30 degree at cut off 20.7 had sensitivity 90.7%, specificity 83.3% and accuracy 88.1% in prediction of CVP ≤ 10 mmHg. Finally, CI of IVC at cut off >31.75 had sensitivity 74.4%, specificity 70.8% and accuracy 73.1% in prediction of CVP ≤ 10 mmHg among the studied cases. Conclusions: Ultrasonographic measurement of venous parameters of IJV provides a useful non-invasive tool for assessment of intravascular volume status in critically ill patients.