This paper presents a study on the impact of unified power-quality conditioner (UPQC) allocation on radial distribution systems. A UPQC consists of a series and a shunt inverter. In UPQC, the series inverter injects a voltage with controllable phase angle in such a way that the voltage magnitude at load end remains unchanged. Due to the phase angle shift, the series inverter participates in load reactive power compensation along with the shunt inverter during healthy operating condition. In the proposed approach, the optimal design parameters of UPQC are determined by minimizing objective functions network power loss, Percentage of Nodes with Under Voltage Problem(PNUVP).These objectives are simultaneously minimized to obtain a set of non-dominated solutions using multi-objective PSO (MOPSO). The results show that a significant amount of power-loss reduction, under voltage mitigation can be obtained with an appropriate placement of the UPQC in a distribution network. The performances of PSO with UPQC and UPQC with Capacitor variants are compared and the better one is used in all subsequent studies.