Distribution system optimisation is defined as satisfying the demand of the system in the most economical, reliable and environment-friendly way while all the related operational or geographical constraints are met. In the case that the future load of the system is intended to be met, the problem is also called “expansion planning” problem. In this paper, the existing researches on distribution system optimisation problem are reviewed from the viewpoint of their used optimisation algorithm, used objectives, used decision variables, load model, case study, planning type and planning period. This review found that although diverse optimisation algorithms have already been applied to distribution system optimisation problem, developing efficient algorithms with the ability of escaping from local optima and finding near-global solutions is required. In particular, development of diversity enhancement strategies for metaheuristics and applying them to this problem seems to be fruitful. This review also found that some aspects of distribution systems such as deregulation and demand side management have not been taken into account in modelling of distribution system optimisation problem.