What are the benefits of biodiversity protection? Why should those benefits be estimated? When should they be estimated … now or across future generations? Where should the benefits be estimated … locally, nationally or internationally? And, of course, how can they be estimated, if at all? This sequence of questions forms the basis of this paper. The specific benefits associated with the provision of biodiversity protection are firstly defined. The role of benefit estimation in the process of making decisions regarding the future use of ecosystem resources is then briefly reviewed noting the importance of biodiversity benefits in that process. The “extent of the market” for biodiversity protection is considered with respect to the beneficiaries across both time and space. Some technical issues arising from the choice between alternative non-market benefit estimation techniques are analysed along with a discussion of the techniques’ collective capabilities to perform the task. References to selected case study results, generated from recent applications of the Choice Modelling technique, are used to illustrate the arguments involved. As a conclusion, it is suggested that research effort should be directed to the task of benefit estimation to determine priorities for the protection of biodiversity.