The exposure characteristics of six polymer resists to 1.5 MeV H+, He+, and O+ ions and 20 keV electrons were measured. The deposited energy per unit volume required to expose a resist was found to vary by up to a factor of ten between electrons and O+ ions. A model was developed which accounts for the variation in terms of the energy distribution around the particle track in conjunction with whether the resist requires the activation of a single site or two adjacent sites to produce exposure.