This paper presents a methodology to develop simplified models to address uncertainties in cap rock integrity assessment to support decision making in the CO(2) storage risk management. Conventional analytical approaches might lead to a misestimation of cap rock failure, whereas conventional numerical approaches are too computer time-consuming regarding the multiple realizations required by an uncertainty analysis. An intermediate solution is then proposed based on the response surface methodology, consisting in estimating the stress state after CO(2) injection as a linear combination of the most influential site parameters. An uncertainty analysis methodology is proposed and illustrated on the Paris Basin case.