In the thesis, the influence of cracking on safety of concrete gravity dams has been analysed. This influence has been studied on the case study of hydroelectric power plant Moste. The mechanical analysis has been performed with a computer program CADAM. The safety of the Moste dam has been analysed for various load combinations, drainage systems, crack heights, and values of horizontal ground accelerations. It has been proved that cracking has an important influence on safety of Moste concrete gravity dam.