Although future widespread use of plug-in electric vehicles (PEVs) will considerably reduce the greenhouse gas emissions, their charging demand will pose significant challenges to the grid. Aggregated charge scheduling of PEVs in parking lots (PLs) can mitigate the challenges, if the size and place of the PLs for PEVs are optimally determined. This paper proposes an optimization-based problem to not only determine the optimal size and place of PLs for PEVs, but also optimally schedule the charge and discharge of PEVs in the located PLs. The operation costs of distribution system, including the cost of purchasing energy from upstream grid and the cost of PEV charging in PLs, are considered as the objective of the proposed optimization problem, subject to the distribution system constraints. The proposed method is examined in a test system, considering different penetration levels for PEVs. In addition, the impact of results is investigated on the reliability of distribution system. The results show that decrements in the total cost of operation may lead to a lower reliability for the distribution system. The sensitivity of the results to the maximum charging rate of the parked PEVs in the located Pis is also reported in this paper. (C) 2018 Elsevier Ltd. All rights reserved.