This paper compares the benefits and costs of nature conversation at three Sites of Special Scientific Interest. Benefits are estimated by contigent valuation (expressed preferences) and also the travel cost method (revealed preferences). Oppurtunity costs are assessed from a financial cost viewpoint, and also in terms of ‘shadow’ prices or social costs. Results indicate that the valuation of wildlife and nature conservation largely depends upon the frame of reference adopted; that social costs are considerably less than financial costs due to the effect of the Common Agricultural Policy; that user benefits are considerably less than financial costs; and non-user benefits must be included to cover even the social costs of nature conservation.