Aim: To evaluate the top and bottom hardness of Hybrid and Nano composites polymerized with Halogen based and Light emitting diode light curing unit and Variation in duration of exposure. Materials and Methodology: Sixty Hybrid resin based composite and sixty Nano composite specimens fabricated in 8mm x 2mm stainless steel molds were used for this study. Using two different light curing units: Halogen Based and Light Emitting Diode. The top surface was polymerized for 20/40/60seconds according to the division of each subgroup. The top surfaces were identified with an indelible marker then specimen will be stored in dry lightproof container. Twenty–four hours later indentation were tested using knoop hardness tester of 100gm load and a dwell time of 10sec.The top and bottom surface were checked. Statistical analysis was done using 2–way ANOVA and the interaction effect were tested by scheffe’s multiple comparison test (p<0.001). Results and conclusion: Results showed that the hybrid and nano resin based composite, for all top and botttom hardness, the hybrid producing much higher knoophardness.( for group A,B). The halogen based light curing units produced harder top and bottom resin based composite surface than light emitting diode curing units.(Group A– sub group A, B).From this study we can conclude that the effect of duration for exposure, presents no significant difference with respect to curing units and type of resin based composites in all groups. .