Thin films of lithium phthalocyanine (PcLi) were prepared by vacuum deposition on a glass substrate at various substrate temperatures. Modifications of the electron spin resonance signal (shape, position) with the substrate temperature are evidenced and explained by means of the x-like --> alpha phase transformation. Moreover, thin films deposited on glass substrate show a strong preferential ordering of the molecules forming columns which are lying in the plane of the substrate, the resulting orientation of the molecules being almost perpendicular to the substrate plane. This preferential ordering results in an anisotropic spin transport depending upon the substrate temperature. It is demonstrated that the demagnetizing field can account for the temperature dependence and the angular variation of the g-factor in PcLi thin films.