The evaluation of environmental vulnerability is one of the key factors in need of consideration during the improvement of decision-making systems and the development of response strategies to radionuclide release into marine regions. Environmental marine modelling has to simultaneously describe the dispersion of radionuclides in water and sediment phases; bioaccumulation of radionuclides in biota and finally, dose assessments. It is obvious that such an approach comes up against the problem of complexity and the need for a large set of parameters. The sensitivity analysis of the model parameters can contribute to a better understanding of experimental data as well as define parameters which can play a key role in the evaluation of environmental vulnerability. In the present paper sensitivity analysis has been carried out using the compartment modelling approach for assessment of the environmental vulnerability as dose to man. The sensitivity analysis shows that the influence of model parameters can vary greatly depending on the concrete radionuclude and on the marine region. It is also shown that the results of the sensitivity parameter analysis can contribute to the process of defining which parameters can play an important role in the dose assessment and the evaluation of environmental vulnerability.