Leksell gamma knife is designed solely for the treatment of brain disorders. It uses stereotactic technique in which several gamma beams are concentrated on a brain tumor. Individual beams are too weak to cause a satisfactory damage to cancerous cells. However with the concentration of several beams from different angels on the target point, it receives the accumulating doses out of all the beams. In this technique healthy neighboring tissues receive the slightest possible dose. Different Leksell gamma knife systems use different techniques for beam concentration. For instance in ‘C’ model of this system, 201 cobalt sources are symmetrically distributed on a hemispherical surface. In rotating model, 30 rotating sources with 60 degrees angular distances are distributed on a hemispherical surface. In this research, using MCNPX code, we simulate two types of this radiotherapy system for computing dose profiles in water phantom and in skull bone phantom. In both models, brain tissue is simulated by water. However in skull bone phantom, a spherical layer is also added as skull. Eventually we investigate dosimetric parameters of static ‘C’ model gamma knife using Snyder real phantom simulation. Then we compare the results with the profile calculated by GP software. In addition, by simulating rotating gamma knife, we investigate its dosimetric differences with static gamma knife.