It is essential to know how livestock select their diet and the factors that influence this diet selection for the development of rational techniques leading to suitable management of pasture. The aim of this study is to determine the main plant species consumed by goats in arid Mediterranean shrublands, and to show how the preference for a plant changes depending on its availability and chemical composition. Plant species that are not very representative within the range of this study or, consequently, in the diet (Teucrium capitatum,Launea laniferaandSideritis leucantha) are shown to be, however, those most selected, and thus in danger of extinction due to the excessive pressure. The speciesAnthyllis cytisoidesis of interest, not only because it is the most abundant in pasture and diet, but also because it is highly palatable. Goats need to change the components of their diet constantly since plant species are significantly more preferred in those zones where they are least available. Plant selection is inversely proportional to the content of Acid Detergent Lignin (ADL). In the remaining nutritional parameters analysed, no significant results were obtained, possibly because of the influence of other variables (i.e. secondary compounds), which were not monitored in this study.