On the basis of a review of the Quaternary sedimentary architecture in the area of Hanoi city (Vietnam), a numerical, deterministic and three-dimensional groundwater flow model has been built for a simulation between 1995 and 2004. The sedimentary architecture has been constructed on the basis of the data from 32 drillings covering the entire Quaternary sequence (but with little sedimentological detail), as well as hydrographical and hydrogeological data. Both steady- and transient-state conditions were tested. Results calculated by the model seem to indicate that the conceptual hypotheses adopted are reasonable for the modelled domain and period. The simulation allows for calculation of the regional groundwater flow trends. It is also used for assessing the relative importance of the various recharge sources of the shallow aquifer system in Hanoi, and for estimating the interactions between groundwater and the Red River.