CdSe/CdS and CdSe/ZnSe core/shell nanostructures dispersed in PVA are prepared by chemical method at room temperature. TEM images show the nanorod and spherical type nature of CdSe/CdS and CdSe/ZnSe core/shell. The linear refractive index (n) and absorption coefficient (a) are calculated from transmittance measurements. Z-scan technique is used to calculate the nonlinear optical parameters such as n(2), beta and chi((3)) . These core/shell nanostructures show two photon absorption mechanism. Third order nonlinear susceptibility is found to be similar to 10(-7) to 10(-8) m(2)/V-2 at 633 nm. Larger value of third order nonlinear susceptibility is due to dielectric and quantum confinement effect. (C) 2015 Published by Elsevier B.V.