Eleven low rank coals from North Bohemian mines were comprehensively characterized by using a number of analytical methods. Along with common proximate and ultimate analysis, spectroscopic techniques, porosity measurement, extractability and swelling in organic solvents were used. Although coals were of similar geological origin, some of their characteristics largely differed from one coal to another. Coals were coprocessed with petroleum vacuum residue at 440 degrees C for 1 h and yields of reaction products and coal conversions were determined. Despite the differences in composition and properties, the coals provided similar conversions and yields of distillable reaction products. A small positive effect on coal conversion was found for ash content and microporosity of coals, However, a small negative effect was found for carbon content, optical reflectance and solvent extractability of coals.