The frequency domain photon migration (FDPM) technique was employed for investigation of particle interactions of dense, bidisperse, polystyrene samples of differring volume ratios of small to large particle sizes. The particle interactions of bidisperse systems were evaluated from the angular integrated structure factors, , which were extracted from FDPM measurements of scattering properties at high volume fractions ranging from 0.1 to 0.3. The FDPM-measured were then compared with theoretical predictions using the full binary hard sphere Percus-Yevick (HSPY) model, as well as the decoupling approximation (DA) and the local monodisperse approximation (LMA) models. The influence of differing volume ratios of colloid sizes on structure factors at differing wavelengths was also investigated. Results show that the interactions between small and large particles significantly impact the structure factors as well as the scattering properties in dense bidisperse colloidal suspensions. Furthermore, the binary HSPY model is most suitable for accounting for particle interactions which predominately arise from volume exclusion effects. Upon use of the binary HSPY model, the particle sizes of the two modes of the bidisperse polystyrene suspensions were recovered from dual wavelength FDPM measurements at high volume fractions (up to 0.3). The FDPM-derived particle sizes are comparable with DLS measurements of individual modes at diluted concentrations (similar to0.001).