Recent years have witnessed the boom of plug-in electric vehicles (PEVs) and the charging facilities. This paper proposes an approach for the co-planning of the electric vehicle charging stations (EVCSs) and energy storage systems (ESSs) in the distribution network. Unlike previous works, each unit for investment is assumed to be a pair of EVCS and ESS and the charging loads are considered flexible. A two-stage stochastic programming model, with the investment problem as the first stage and optimal operation problems of EVCSs and ESSs as the second stage, is formulated by generating representative scenarios of base load and distributed generations. To deal with heavy computational burden, the generalized Benders decomposition (GBD) algorithm is then adopted. The effectiveness of the methodology is demonstrated by the conducted numerical experiments.