We aimed to clarify the factors that affect Japanese hare (Lepus brachyurus) densities and habitat availability in certain vegetation types. Using fecal pellet counts, we found that hare densities and habitat availability were higher in open–tree-canopy habitats with a dense ground cover of herbs and grasses, such as cleared areas in artificial forests. However, when we examined the relationships between fecal pellets as an indicator of hare density and various attributes of forest floor vegetation, no vegetation parameters had a significant correlation with fecal pellets among different plant communities. Thus, it is difficult to predict hare density based on forest floor vegetation, in general. However, in seven Japanese cedar (Cryptomeria japonica) plantation sites, high herb volume index and a low degree of canopy closure, calculated from fisheye-lens photographs, had a significant correlation with fecal pellet density (P = 0.029 and 0.006, respectively). Based on the relationships between fecal pellets and certain forest attributes (e.g., stand height and diameter at breast height of trees), we determined that fecal pellet density was higher in young stands in these plantations. This is likely because young stands have a larger volume of herbaceous species that provide food and shelter for hares, owing to the bright ground conditions resulting from the relatively open canopy. Appropriate plantation control such as cutting and planting trees is important for habitat conservation of L. brachyurus, because planted C. japonica forest occupies more than half of artificial forests in Japan.