In this paper are presented the results obtained from a nonlinear seismic analysis of concrete gravity dams. Three dams with different heights will be studied under the effect of several earthquake ground motions. The fluid-structure interaction will be considered using the added mass concept of Westergraad is used to simulate the fluid-structure interaction with the foundation assumed to be rigid. The smeared cracking approach is used to model the initiation and propagation of cracks through the dams. The response of the dam is characterized by evaluating modal characteristics, displacements and crack patterns. The results obtained will allow having an insight into the expected behavior of concrete dams under future expected earthquakes and indicate that dynamic characteristics of a dam and the frequency content of the ground motions are a couple of the key parameters to consider when assessing the seismic safety of concrete gravity dams.