Developmental monetary benefits of coast artificialisation projects are rarely confronted with the environmental benefits that its conservation may entail. As a consequence, policy-makers often face decision making processes in which monetary benefits have to be balanced with physical impacts ending up in undervaluation or overvaluation of environmental aspects. Non-market valuation of coastal and marine resources is thus a growing concern in the assessment of cost-benefit analysis of coastal developmental projects. This paper attempts to estimate the effects on peoples utility of the potential environmental impacts of a new seaport in Pasaia, Spain. A choice modelling technique is proposed as a means of estimating marginal impacts for different environmental attributes of mount Jaizkibel, namely its landscape, flora, avifauna and seabed. The results from a multinomial logit model reveal that, on average, individuals would pay 1.39 euros for a one percentage protection of its landscape; 0.87 euros for protecting its flora; 0.68 euros for protecting its avifauna; and 0.63 euros for protecting its seabed.