Background: Central venous cannulation is an invasive procedure commonly used by many physicians. The aim of this study was to evaluate the effects of the right lateral tilt position on the cross-sectional area and size of the right internal jugular vein, and the relationship between the right internal jugular vein and the carotid artery. Method: Forty healthy volunteers aged over 18 years were included in this prospective, observational study. The right internal jugular vein cross-sectional area and the anatomic relationship with the carotid artery were assessed using ultrasound imaging. This measurement was repeated for four positions (baseline position, 10° right tilt position, 10° Trendelenburg position, and 10° right tilt + 10° Trendelenburg position). The head was rotated 30° to the contralateral side in all patients. Results: The mean (standard deviation) right internal jugular vein cross-sectional area, transverse diameter, and anteroposterior diameter were significantly increased with the Trendelenburg position and 10° right tilt + 10° Trendelenburg position (p < 0.05). There were no significant differences in right internal jugular vein cross-sectional area, transverse diameter, and anteroposterior diameter between the baseline position and 10° right tilt position (p > 0.05). Conclusion: We found that the right lateral tilt position had no effect on the internal jugular vein cross-sectional area and that the Trendelenburg position was still the most valid position for safely increasing the right internal jugular vein cross-sectional area.