Objective The aim of the present study was to evaluate the effect of curing mode on marginal adaptation of low shrink resin composite resin under objectives of two different resin composites, two different curing modes, two different cavity designs and three different storage times. Materials and Methods One hundred and twenty freshly extracted posterior teeth for tested material (silorane and kalore resin composite). Samples were light cured with two light curing units; quartz tungsten halogen (QTH) and light emitting diodes (LED). Microleakage test was measured on top and bottom surface of each sample. Statistical analysis was done using two ways ANOVA. Results There was a significant influence of the materials and their interaction with LCU on the microleakage value (P>0.05), silorane resins composite have better marginal adaptation to tooth structure than kalore resin composite. LED light cure give better marginal adaptation than QTH light cure.  Conclusion Marginal adaptation improved by using silorane than other formulation used. Elipar light curing source improve sufficient depth of cure in cavity depth at 5mm. Both the restorative materials tested in the study had significant difference microleakage especially along the gingival seat in class II cavity.