Background: Laryngeal mask airway (LMA)-Classic (CLMA) and Laryngeal mask airway (LMA)-Proseal (PLMA) are commonly used supraglottic devices for different kind of surgeries. We compared oropharyngeal leak pressure, intracuff pressure and anatomical position for LMA-Proseal and LMA-classic in four different head and neck positions: neutral, flexion, extension and left lateral rotation. Materials and Methods: LMA-Proseal and LMA-Classic were inserted randomly in 100 adult patients. Oropharyngeal leak pressure, intracuff pressure and anatomical position of the airway were recorded in four head and neck positions (neutral first, then flexion, extension and left lateral rotation). Results: Compared with neutral position, oropharyngeal leak pressure for both LMA-Proseal and LMA-Classic was higher in flexion and left lateral rotation but lower in extension (all p values <0.005). Changes in head-neck position did not alter the anatomical position of the airway. Oropharyngeal leak pressure was always higher for LMA-Proseal than for LMA-Classic (p value < 0.001). Conclusion: The anatomical position of LMA-Proseal and LMA-Classic is stable in different head-neck positions, but head-neck flexion and left rotation are associated with an increase and head-neck extension is associated with a decrease in oropharyngeal leak pressure and intracuff pressure as compared to neutral position. LMA-Proseal forms a better seal than LMA-Classic in all the different head and neck positions.