In this work the spectroscopic and microscopic studies of dodecaphenyl POSS thin films are presented. Thin films have been deposited using molecular beam technique. Due to thermal properties – relatively low sublimation temperature and preservation of molecular structure – cage type silsesquioxanes are perfect to fabricate a thin film by means of physical vapor deposition.PhT 12 thin films with thickness varying from 40nm up to 100nm, deposited on a Si(100) surface, were studied under high vacuum conditions. The research was focused on the influence of post deposition annealing (from 100°C up to 200°C) on molecular structure as well as thin film roughness and optical properties.A wide range of measuring methods were applied for thin film studies. Fourier Transform Infrared Spectroscopy (FTIR) was used in order to learn molecular structure and stability, Ellipsometry for thin film thickness and uniformity, Grazing Incidence X-ray Diffraction (GIXD) for thin film long range order investigation and finally Atomic Force Microscopy (AFM) for visual confirmation of drawn conclusions.