Studies were made of the properties and structure of hard coals taken from the borehole Niedobczyce IG-1 in Rybnik Coal District (Upper Silesian Coal Basin) collected from a depth of up to 1830 m, Coals occurring there vary from gas flame (611-VII)(2) to orthocoking (435-VB) types, Assessment of changes in quality and structure of the coals was based on the results of technical and elementary analyses, tests on coking properties and petrographic;analysis, In the tested borehole the changes in the properties of coal take place in conformity with the Hilt rule [1] with the exception of the Michalkowice overthrust strata, occurring however, in a relatively narrow and shallowest zone of the borehole. An interpretation of the changes ascertained is formulated and certain relations between the properties and the structure of coal were established.