Funds available for biodiversity projects are scarce. Choices must therefore be made on how to use limited resources most effectively, and such decisions should be based on clear and measurable objectives for achievement. Biodiversity projects should be evaluated to determine if the use of scarce resources has achieved the objective (effectiveness), and if the projects achieve the objective at lower cost than alternative uses of the resources (cost effectiveness). Project selection and evaluation methods are used patchily by biodiversity project providers and researchers. We provide an introduction to project selection and evaluation; point to the range of selection and evaluation methods available; ask where they are best applied; and focus attention on the need to overcome the hurdles to adoption and continuation of project selection and evaluation methods.