Acid-etched cast metal resin-bonded retainers require resin luting agents with film thicknesses similar to dental cements to allow complete seating of frameworks without the need for post-bonding adjustments. Conventional cements, restorative resins, and resin cements were compared in terms of film thickness by using the American Dental Association Specification No. 8 for zinc phosphate cement. Most of the resin luting agents had film thicknesses of 20 to 40 microns. Working time was seen to affect film thickness. The particle size of one resin was also examined under scanning electron micrograph.