MIDA is a distributed model for hydrological processes at the basin scale, the structure of which is suited to small basins of mountainous Mediterranean coastal areas. The underlying philosophy of the model is a distributed conceptual approach in which geomorphological scaling relationships are used, fully supported by a Geographical Information System. The sensitivity of the model response to some variable conceptual and global parameters and its performance across some different land-use and climatological conditions are analyzed. The analysis reveals a high sensitivity to some parameters related to infiltration and runoff generation (soil cover thickness on hillslope and saturated hydraulic conductivity) and to land-use features, while change in discretization levels seems to have less influence on predicted discharge.