Thin films with chiral or helical microstructures exhibit circular birefringence effects. Glancing angle deposition (GLAD) is a fabrication method capable of producing chiral thin films with controllable porosity and microstructure. In this paper, the effects of porosity on the circular birefringence exhibited by helical TiO<sub>2</sub> films are presented. Transmittance measurements reveal two optimal film growth angles: one corresponding to a maximum in form birefringence and another corresponding to strong anisotropic scattering. Reflectance data support the transmittance measurements in the regime where scattering is minimized.