A comparison of the structure and phase composition of a recently synthesized carborane-containing copolymer and its wholly organic analogue was carried out by DSC and X-ray analysis in a wide temperature range between 20-300 degrees C. It is found that the incorporation of 10 mol-% of m-carboranedicarboxylic units in the polymer prepared from 4,4'-dihydroxybiphenyl and sebacic acid, acting as mesogen and flexible spacer, respectively, leads to the formation of a columnar mesophase at elevated temperatures. This newly observed phase occurs in addition to the crystalline and liquid crystalline smectic phases known for the wholly organic analogue.