This article explores basic constraints on the nature and appreciation of cinematic adaptations. An adaptation, it is argued, is a work that has been intentionally based on a source work and that faithfully and overtly imitates many of this source's characteristic features, while diverging from it in other respects. Comparisons between an adaptation and its source(s) are essential to the appreciation of adaptations as such. In spite of many adaptation theorists' claims to the contrary, some of the comparisons essential to the appreciation of adaptations as such pertain to various kinds of fidelity and to the ways in which similar types of artistic goals and problems are taken up in an adaptation and its source(s).