Over the past several years a class of silver‐doped GeSexmaterials has received attention as a high gamma, negative resist. The columnar structure of the GeSexfilms is believed to be linked to some of the lithographic properties of the resist. However, the mechanism of Ag incorporation is not well understood. In this paper we report secondary ion mass spectroscopy (SIMS) observations of the Ag migration in GeSe2films. Furthermore, we have found evidence for a fast Ag diffusion effect in GeSe2. These findings are consistent with a columnar GeSe2structure. The Ag concentration depth profile in 3000‐ and 6000‐Å‐thick films of GeSe2on substrates consisting of 300 Å of Ta on silicon wafers has been studied by SIMS. An O+2primary beam was used in the SIMS analysis, with the bombardment energy reduced to 3 keV to minimize possible beam‐induced effects and to increase the depth resolution. The Ag2Se/GeSe2resist was exposed by an unfiltered mercury arc source and received doses ranging from 0 to 2 J/cm2. The unreacted Ag2Se was stripped prior to the SIMS analysis. The Ag incorporation was found to increase rapidly with exposure first, and then saturate about 1 J/cm2. But instead of Ag being uniformly distributed through the GeSe2films, its concentration peaks both near the top surface and at the substrate interface. The anomalous Ag peak at the substrate interface indicates that Ag diffuses far beyond the penetration depth of the radiation and presumably piles up in front of the Ta diffusion barrier. Moreover, with the same exposure, the anomalous Ag peaks are identical in both the 3000‐ and 6000‐Å‐thick films. These results are consistent with the model of Ag diffusion through the columnar structure of GeSe2, an extremely fast path in regions between the columns extending through the film, and a slower diffusion component in the denser regions within the columns.