Background:The primary aim of this study was to compare the incidence of accidental arterial puncture during right internal jugular vein (RIJV) cannulation with and without ultrasound guidance (USG). The secondary end points were to assess if USG improves the chances of successful first pass cannulation and if BMI has an impact on incidence of arterial puncture and the number of attempts that are to be made for successful cannulation.Settings and Design:Prospective observational study performed at a single tertiary cardiac care center. Material and methods: 255 consecutive adult and pediatric cardiac surgical patients were included. In Group I (n = 124) USG was used for the right internal jugular vein cannulation and in Group II (n = 81) it was not used. There were 135 adult patients and 70 pediatric patients. Statistical analysis: Demographic and categorical data were analyzed using Student ‘t’ test and chi- square test was used for qualitative variables.Results:The overall incidence of accidental arterial puncture in the entire study population was significantly higher when ultrasound guidance was not used (P < 0.001). In subgroup analysis, incidence of arterial puncture was significant in both adult (P = 0.03) and pediatric patients (P < 0.001) without USG. First attempt cannulation was more often possible in pediatric patients under USG (P = 0.03). In adult patients USG did not improve first attempt cannulation except in underweight patients.Conclusions:USG helped in the avoidance of inadvertent arterial puncture during RIJV cannulation and simultaneously improved the chances of first attempt cannulation in pediatric and in underweight adult cardiac surgical patients.