Abstarct: Shunt capacitors are usually installed in a distribution system to reduce power losses, improve voltage profile, increase capacities of distribution lines and transformers, and improve power factor. Power electronic and electromagnetic devices generate and inject considerable harmonic currents into the power system. If the shunt capacitors are not properly selected and placed in the power system, they can amplify these harmonics and can cause harmonic parallel resonances. Therefore, analyses, simulation, and optimal selection of capacitor banks under harmonic conditions should be investigated. The purpose of this thesis is to find the optimal placement and sizing of fixed capacitor banks in radial distribution networks in the presence of current harmonics. In this thesis, the objective function includes the cost of power losses, energy losses, and cost of capacitor banks with constraints include voltage limits, number, size and locations of installed capacitors, and the power quality limits consist of total harmonic distortion and reactive power injection from capacitors. In addition, the effect of load modeling in the capacitor placement is studied in this thesis. The proposed method has employed genetic and particle swarm algorithm to find the optimal placement of the capacitors. The proposed algorithms is simulated on the 33 and 69-bus test system. The results of the simulation show the ability of the proposed algorithms to locate the capacitors in the presence of linear and non-linear loads. Since the voltage dependent loads are considered in the simulation, The results show that the load modeling affects the placement of the capacitors.