Nitrogen-containing heterocycles and cellulose are a promising pair of materials studied for use as polyelectrolytic membranes in fuel cells. However, the effect of the amount of heterocycle applied to the cellulosic substrate on the proton conductivity value is yet unknown. In order to provide new insights, in this paper we investigated the proton conductivity of three types of cellulose-based films that contain varying amounts of 1-hydroxybenzotriazole (HBT), a model heterocycle, in close correlation with other film surface properties such as X-ray diffraction, scanning electron microscopy (SEM), and atomic force microscopy (AFM). Furthermore, the effects of changing the kind of cellulosic surface on mechanical characteristics were assessed.