This article discusses the possibility of optimizing a particular postal transportation network within the scope of the main mail processing and distribution centres in Žilina, one of four main mail processing and distribution centres of the national postal operator in Slovakia – Slovenská pošta (referred to here, in English, as the Slovak Post). The authors compare the 3-level model of postal transportation network with the 4-level model of postal transportation network that is currently used in areas other than Žilina. When comparing both models, the authors also takes into account the processing operations of postal items required before the mail is delivered to its addressee – both models accept the technological procedures of processing and handling postal items. In addition, the authors of the presented article solves the allocated task through the construction of the distance matrix to find out if the actual location of the main mail processing and distribution centre and its facilities in the city of Žilina is optimal, from the point of view of transportation distance from this centre and the other supporting processing centres located at the second and third levels respectively within the analysed postal transportation network models.