The influence of incident polarized light, refractive index, and size parameter of the scatterer on achievable resolution and contrast (image quality) of polarization-gated transillumination imaging in turbid media is reported here. Differential polarization detection led to significant improvement of image quality of an object embedded in a medium of small-sized scatterers (diameter D<<lambda, isotropic scattering medium, anisotropy parameter g<or=0.2), especially using circular polarization. In contrast, for anisotropic scattering media composed of larger-sized scatterers (D>or=lambda,g>or=0.7), the improvement in image quality was less pronounced using either linear or circular polarization gating when the refractive index of the scatterer was high (ns=1.59), but for a lower value of refractive index (ns=1.37), image quality improved with the differential circular polarization gating. We offer a plausible explanation for these observations.