The phase behavior and structures of liquid crystals in aqueous solution of Pluronic copolymers (P85; (PEO)(26)(PPO)(40)(PEO)(26), P105; (PEO)(37) (PPO)(58)(PEO)(37)) mixed with nonionic surfactants (C12EO5, C18:1EO5) were investigated. In a binary water/P85 system, the sequence of self-assemblies is similar to that of the aqueous P105 system, and aqueous micellar solution, micellar cubic, hexagonal, and lamellar phases are successively formed. P85 forms a single lamellar liquid crystal (Lalpha) with C12EO5 in water at high concentration, whereas two L. phases coexist in the water/P105/C12EO5 system. Two coexisting lamellar phases become identical at a critical point upon replacing P105 with P85. We calculated the average cross-sectional area, as, at the hydrophobic interface using SAXS data. The partial molecular areas of copolymer, a(S)(P), and surfactant, a(S)(S), were also evaluated from a(S) values obtained at different compositions of the copolymer- surfactant mixture. It was found that a(S)(P) decreases and a(S)(S) slightly increases in the copolymer L-alpha phase with increasing the surfactant mixing fraction in the copolymer-surfactant mixture.