The existence of allometric relationships between home-range size and body mass was tested for 34 Italian mammals and 106 Italian birds. These allometries were investigated in relation to a carnivorous, omnivorous or herbivorous diet and, in the case of birds, also territoriality. Initially, non-phylogenetic comparative analyses were undertaken by fitting general linear models to data on average home-range size and average body mass obtained from the literature. Then, two phylogenetic trees for the studied species of mammals and birds were reconstructed and phylogenetic independent contrasts were applied in order to determine the influence of phylogeny on these relationships. For mammals, the type of diet proved to be a determining factor in defining the relationship between home-range size and body mass. Significant allometries were found with both conventional and phylogenetic analyses in all trophic groups. The results emphasized the importance of the spatial distribution of resources in understanding these allometries. For birds, conventional analysis showed significant relationships between home-range size and body mass, and pointed to the importance of both diet and territorial systems in understanding these allometries. After controlling for phylogeny, significant allometries were found only for those birds for which information on the size of their feeding territory was available. Regardless of the complexity of factors influencing the home-range size of a species, the outcomes of this study support the notion of the existence of an allometry between home-range size and body mass among Italian mammals and birds, suggesting that further developments of this area of investigation may prove worthwhile.