The main objective of the study is to determine the correlation between random reflectance of ulminite B/collotelinite and chemical and technological parameters in Polish low-rank coals. The study includes results from 284 samples of humic low-rank coal from Polish deposits tested by the author and supplemented with data from the literature. Research on the properties of different types of coal include: technical analysis, physico-chemical and petrographic analysis. Among the studied deposits, the average random reflectance (Rr) is 0.28, with a standard deviation of 0.06 and the coefficient of variation at 20%. Gross calorific value in the tested coal varies from 7.25 MJ/kg to 26.30 MJ/kg, with average value of 12.46 MJ/kg. Average total moisture in Polish low-rank coal deposits is 47.8% and ranges from 15% up to 60%. Carbon content in the tested coal recalculated to dry ash-free basis varies from 56.4% to 79.0% while on average it is 68.1%. Basic parameters of Polish low-rank coal are characterized by low variability, while gross calorific value and carbon content are of very low variability. The highest variability is observed in case of ash content and sulphur content. The correlation between random reflectance, gross calorific value and carbon content is very high. There is high correlation between moisture, net calorific value and random reflectance. The analysis shows that it is possible to calculate random reflectance of ulminite B/collotelinite from gross calorific value, carbon content and total moisture with a correlation coefficient equal to 0.97. By analyzing the correlation between the measures of the degree of coalification and using multiple regression, it has been found that the suborder of Polish lignite can be determined with use of the random reflectance of ulminite B/collotelinite. Based on the results of multiple regression, it is proposed that the boundary between low-rank C (soft brown coal) and low-rank B (dull brown coal) for Polish low-rank coal should be set at a random reflectance of ulminite B equal to 0.35%. (C) 2013 Elsevier Ltd. All rights reserved.