In stream ecosystems, bryophytes greatly increase substrate heterogeneity and support a high density and diversity of lotic primary producers, such as epiphytic algae. However, there is little information about how the spatial distribution and density of epiphytic diatoms varies with respect to bryophyte morphology. This study examined epiphytic diatom communities from the contrasting bryophyte morphologies of mosses and liverworts. We predicted that mosses, with morphologies that create more crevices, would have a higher density of epiphytic diatoms than liverworts, with leaves highly exposed to the turbulence of the stream current. Six species of bryophytes (two mosses and four liverworts) were collected from streams in the Great Smoky Mountains National Park, and 37 species of epiphytic diatoms were identified on these bryophytes. Diatom density was significantly higher on the adaxial leaf surface of mosses compared to the abaxial leaf area (ANOVA, df = 29, P < 0.001). There was no difference in diatom density on either the adaxial or abaxial leaf surfaces of liverworts, and these diatom densities were statistically identical to the density observed on the abaxial surface of moss leaves. The findings of our study support our hypothesis that the morphology of mosses, comprised of leafy whorls, provides a greater level of protection from disturbance than the open, flat nature of leafy liverworts. These findings emphasize that differences in microscale habitats can result in varying diatom distribution and density that may be critical to food-web interactions, such as grazing.