DBAR measurements were made on nanometre thick organic films prepared on a gold substrate using the Langmuir-Blodgett technique. The thickness per layer of the resulting films, (omega -tricosenoic acid, (12,8) diacetylone (monomer) and (12,8) polydiacetylene (polymer) is the same (30 Angstrom to within similar to 10%) but each has widely differing electronic properties. The purpose of the study was to investigate the influence on the annihilation parameters of changing the molecule of the film itself and the conditions under which the films are formed. Significant differences were observed in the energy dependence of the W width parameter when any of the two factors were changed. Data taken for film thicknesses of 1 and 19 layers were used to suggest the existence of an interface state. Although this appears to be determined primarily by the nature of the COOH group that is involved in the attachment, there is also a dependence on the electronic nature of the film itself.