The cooling system of an injection mold serves a substantial role in the process of plastic injection. It is responsible for efficient dissipation of heat from the injection mold, generated by the plasticized material which during the injection phase is introduced into the mold. Apart from rapid heat dissipation, it is important to achieve uniform distribution of temperatures on the surface of the molding cavity. This study focuses on the phenomenon of lime scale deposition in injection mold cooling systems. Lime scale deposition results in reduction of the cooling canal’s section diameter, as well as a clear reduction in cooling efficiency due to its lowered thermal conductivity. The study specifies the influence of many factors (geometry of the cooling system and molded piece, coolant temperature, type of plastic material) on the utilization of the injection mold as a result of the occurrence of lime scale in the cooling system. The conducted numerical simulations have allowed to account for the impact of the deposit layer’s thickness on the distribution of temperatures on the molding cavity’s surface, the average injection mold temperature, as well as the time required to solidify the plastic material products