Open Gromov-Witten invariants are essential ingredients of Lagrangian-Floer intersection theory, and they serve as quantum corrections in mirror symmetry from SYZ viewpoint. They are difficult to compute in general due to non-trivial obstructions in the moduli. In this talk, I will illustrate by examples how to compute open Gromov-Witten invariants of toric manifolds, by relating them to closed Gromov-Witten invariants which are better understood. This also gives an enumerative meaning of mirror maps. This is joint work with Kwokwai Chan, Naichung Leung and Hsian-Hua Tseng.