The paper presents CFD simulations of high pressure hydrogen release and dispersion inside thestorage room of realistic hydrogen refueling station and comparison to experimental data. The experiments were those reported by Tanaka et al. (2005), carried out inside an enclosure 5 m wide, 6 m long and 4 m high having 1 m high ventilation opening on all sidewalls (half or fully open) containing an array of 35 x 250 L cylinders. The scenarios investigated were 40 MPa storage pressure horizontal releases from the center of the room from one cylinder with orifices of diameters 0.8, 1.6 and 8 mm. The release calculations were performed using GAJET integral code. The CFD dispersion simulations were performed using the ADREA-HF CFD code. The structure of the flow and the mixing patterns were also investigated by presenting the predicted hydrogen concentration field. Finally, the effects of release parameters, natural ventilation and wind conditions were analyzed too.