We studied the effect of codlemone geometric isomers (E,Z)-, (Z,E)-, and (Z,Z)-8,10-dodecadienol on sex attraction of male codling moth, Cydia pomonella (L.), in the field and in a wind tunnel. The use of an ultrasound evaporator made it possible to apply known rates of compound at defined isomeric purity. In the wind tunnel, 5, 20, and 100% addition of Z,E isomer to (E,E) -8,10-dodecadienol (codlemone) slightly increased male night response. However, field captures with these blends were not significantly different from codlemone alone. A 20 and 100% addition of E,Z isomer decreased male landings on the odor source in the wind tunnel and trap captures in the field; Z,Z had an antagonistic effect at 100%. The equilibrium isomer blend (100% EB; 26% E,Z; 20% Z,E; 5% Z,Z) strongly reduced male attraction. The behavioral effect of isomerization of codlemone in dispenser materials used for mating disruption has to be taken into consideration.