Purpose: A radiopaque self-polymerizing adhesive resin was prepared by incorporating bismuth subcarbonate-poly(methyl methacrylate) prepolymerized composite (BS-PMMA) into an acrylic resin. The purpose of this study was to evaluate the radiopacity of prepared resins.Methods: As a radiopaque component, a composite containing 50% bismuth subcarbonate was used, and other metal compounds were adopted as controls. They were added to finely pulverized PMMA. Specimens were prepared from the powders, methyl methacrylate (MMA) monomer with 5% 4-methacryloyloxyethyl trimellitate anhydride (4-META) and tri-n-butylborane derivative (TBB) by mixing. Radiographs of the specimens were taken together with tooth slices and aluminum step wedges. The density of the specimens was determined with a densitometer and was expressed in terms of the equivalent thickness of aluminum per 2.0 mm unit thickness of specimen. Results: The radiopacity value of BS-PMMA-based specimen was 3.7 mm Al / 2.0 mm specimen, which was nearly the same value as enamel (3.7) and exceeded the values of dentin (2.0). Conclusion: BS-PMMA composite and bismuth compounds are useful as a radiopaque additive for the acrylic resin.