In this work, thin films of tetrafluorosubstituted cobalt phthalocyanine (CoPcF 4 ) were prepared by organic molecular beam deposition and their structure was studied using UV-vis, polarization dependent Raman spectroscopy, XRD and atomic force microscopy. Quantum chemical calculations (DFT) have been employed in order to determine the detailed assignment of the bands in the CoPcF 4 IR and Raman spectra. The electrical sensor response of CoPcF 4 films to ammonia vapours was investigated and compared with that of unsubstituted cobalt phthalocyanine films. In order to explain the difference in sensitivity of the unsubstituted and fluorinated phthalocyanines to ammonia, the nature and properties of chemical binding between CoPc derivatives and NH 3 were described by quantum-chemical calculations utilizing DFT method. The effect of post-deposition annealing on surface morphology and gas sensing properties of CoPcF 4 films was also studied.