The unprecedented occurrence of two different kinds of uniplanar orientation by solution casting, observed for syndiotactic polystyrene (s-PS) films, has been rationalized in terms of host-guest interactions into molecular complex phases. Correlation lengths along different crystallographic directions (D-hkl), of molecular complex crystalline domains of s-PS with several different guest molecules, have been investigated by wide-angle X-ray diffraction. The chemical nature of the guest has a strong influence on the correlation length perpendicular to the ac plane (i.e., perpendicular to the layers of close-packed enantiomorphous helices) and a weak influence on the correlation lengths along a and c (chain) axes. Less and more favorable host-guest interactions lead to molecular complex domains with low and high degree of order perpendicular to the ac layers (D-010 < 6 nm and D-010 > 7 nm) and generate cast films with uniplanar (010) and (002) orientations, respectively.