Background: The internal jugular vein (IJV) is widely used to assess the jugular venous pressure. One can roughly estimate the pressure in the right atrium by looking at the pulsations and their height in the IJV. The aim of this work was to assess technical ultrasound and color Doppler errors in assessment of IJV by comparing sonographic parameters with those obtained from other imaging examination like CT. Methods: This prospective study was carried out on patients with CT for pathological neck lesions and normal IJV who came for CT examination of the neck for different pathological lesions not related to disease in jugular vein. All patients were subjected to clinical examination and ultrasound and color doppler examination of IJV. Results: The interclass agreement coefficient between AP diameter of RT IJV (supine position) by CT and by U/S is 0.919 (CI: 0.847-0.957) with significant value (p < 0.001). Also, the interclass agreement coefficient between AP diameter of LT IJV (supine position) by CT and by U/S is 0.984 (CI: 0.969-0.991) with significant value (p < 0.001). Conclusions: technical ultrasound errors in assessment of internal jugular vein can lead to errors in the results, erroneous diagnosis of pseudotumor or developmental anomaly. Measuring anteroposterior diameter of right and left IJV while patient supine with Valsalva maneuver or while patient sitting give inaccurate results when compared with CT measurements as a gold standard method for measurement.