Due to deregulation and restructuring in many countries, it is expected that the amount of small-scale generations connected to the distribution networks will increase. So, it is necessary that the impact of these kinds of generators on Volt/Var control should be investigated. This paper presents a new approach to Volt/Var control in distribution systems with Distributed Generation (DG). It has been shown that DG can improve the entire performance of a network system, by means of better control and decreasing losses. In this approach, the Genetic Algorithm (GA) has been used as the optimization method, where the amount of DG and its controlling parameters, the voltage regulators situation, the status of the load tap changers and, finally, the amount of switched capacitor, have been assumed as state variables. This method is tested on IEEE 34 bus radial distribution test feeders and a rural distribution network. The results are presented and it is shown that in the case of the selection of a correct location for DG, the system losses can be decreased by up to 70%.