— The formation of " hydrothermal resources " , a term including mineral and geothermal resources, is the result of thermal, hydraulic, mechanical and chemical processes. Accounting for all of them (THMC modeling) is not an easy task since a large number of variables are unknown. However, when only hydraulic and thermal processes are selected, numerical tools such as the " Rock Alteration Index " can be used to predict locations of the most probable mineralized zones. As an example, 3D numerical models of the Tighza pluton (Morocco) demonstrate that computed mineralized zones correspond to those found in the field. Using geological, petrophysical data and measured temperatures, numerical simulation of the Soultz-sous-Forêts geothermal system (France) helped to understand how fluid circulation in the shallow crust is controlled. Besides reproducing temperature profiles, the obtained numerical models were also used to predict the depth and the temperature of a previously suspected anomaly (Rittershoffen area). It turned out that this anomaly (160°C at a depth of 2500m) was confirmed at the same time by temperature measurements in a borehole. Numerical modeling of hydrothermal processes should thus be considered as a predictive tool in exploration strategies. 