Introduction: Head and Neck tumors are mainly treated with concurrent chemoradiation. Treatment delivery with Megavoltage beam has the advantage of skin sparing effect but still skin reactions have been a major side effect since 2D era. Initially these reactions were due to the delivery with bilateral opposed portals but with advent of IMRT/ VMAT, it has been possible to escalate the tumor dose with the need of strict immobilization with thermoplastic mask. This thermoplastic mask may have a bolus effect and can result in increase in surface dose resulting in skin reactions. The aim of this study was to evaluate if any bolus effect of thermoplastic mask exists. Materials and Methods: A total of 15 patients of histologically proven carcinoma oropharynx and hypopharynx were taken. Patients were scanned for planning CT with thermoplastic mask. Another scan was taken in the same position but without thermoplastic mask. Same contouring and planning were done on both the scans. Plans were made and ascertained that all OAR’s and target volumes should get similar doses. Skin contoured on both the scans was evaluated for the dose received. Results: Mean dose received by skin in patients with thermoplastic mask was 48.15 GY while Mean dose received by skin in patients without thermoplastic mask was 43.18 GY. A paired t-test was applied on the dataset which revealed a statistically significant difference between the skin doses with and without mask with a p value of < 0.05. Conclusion: Increase in skin dose can be attributed of the bolus effect of thermoplastic mask. This bolus effect should be considered once high dose to skin is observed during planning or patient develops skin reaction.