EN
Self-consistent field ab initio calculations were performed in order to determine the electronic structure of iron phthalocyanine (FePc) and its changes under interaction with the O_{2} molecule. The experimental evidence related to O_{2} adsorption on phthalocyanine plane was confirmed. The possible charge transfer between phthalocyanine and O_{2} molecule is briefly discussed. Considerable displacement of energy levels in the case of oxygen adsorption on FePc plane has been noticed.