A comparative study on ecology of rodents was carried out in Arbaminch Forest and nearby farmlands from August, 2005 to April, 2006 in Ethiopia. Six different types of habitats, four from natural forest and two from farmlands were randomly selected. In each habitat type, one representative trapping grid was randomly selected for live trapping. In addition, rodents were also surveyed from each habitat by snap trapping. Sixteen species of small mammals (fourteen rodents and two shrews) were recorded from the study area. Of these four rodent species (M. natalensis, A. dembeensis M. musculus and Hystrix cristata) were recoded as pest species of maize crops in farmlands. The distribution of species varied from habitat to habitat and season to season.