The objective of this study is to compare the marginal seal of Class II cavities restored with indirect inlays constructed on glass ionomer cement linings having different curing properties. Also the effect of acid-etching of these liners on microleakage was investigated. Mesio-occlusal and disto-occlusal cavities in 80 extracted human molars having the cervical floor below the cementoenamel junction were prepared (n:160). Half of the preparations were restored with Ceramco II porcelain and the rest with SR-Isosit resin inlay material. Liners as light curing Ionoseal light+chemically curing LCL 8 and Zionomer and chemically curing Ketac-Bond glass ionomer cements (GICs) were used. On mesial preparations GICs were acid-etched but were not on distal preparations. All inlays were cemented with Ultrabond composite material. After thermocycling the teeth were placed in a basic fuchsin dye solution for 24 h, then each tooth was sectioned. By using a stereomicroscope the extent of marginal leakage was scored and statistically evaluated. Microleakage was observed beneath all GIC linings and was more extensive between light curing GIC/dentine interface. By acid-etching of GICs the microleakage between GIC/dentine interface was increased significantly. Whether acid-etching was applied or not a significantly increased microleakage was recorded between chemically curing GIC/composite interfaces. Although the marginal microleakage was witnessed in both inlays, it appeared that porcelain inlays provided a better marginal seal, in comparison to SR-Isosit inlays.