The Swedish Radiation Safety Authority (SSM) has reviewed the long-term safety analysis of a license application for a KBS-3 repository submitted by the Swedish Nuclear Fuel and Waste Management Co. (SKB). In the safety case the hydrogeological analysis is important, extensive and complex. Careful planning and execution is needed for an effective review. The review addressed the different steps in the hydrogeological analysis, including site investigation, conceptual understanding, modelling of the site, and the prediction of the hydrogeological evolution of the repository. The hydrogeological analysis is interwoven with several other disciplines linked to it by different parameters. The Swedish regulations need to be interpreted in view of hydrogeology, since there are no particular such requirements. SSM has made an in-depth review and assessment including in-house and external experts. The objective of this paper is to describe the planning and execution of SSM’s hydrogeological review to discuss lessons learnt that can be applied to the review of safety cases both when it comes to hydrogeology and to other technical disciplines that are interlinked to several parts of a safety case. Moreover, the paper discusses information that can be important to include in a safety case to obtain an efficient review.