This paper presents geochemical characteristics of 35 samples of Miocene lignites and gangue sediments (clays) sampled in the Konin and Turoszow Brown Coal Basins (Poland). Lignites belonged to xylitic, detro-xylitic, detritic and fusitic lithotypes. Organic geochemistry of them were investigated using such methods as Rock Eval Pyrolysis, gas chromatography-mass spectrometry of separated aliphatic hydrocarbons, compounds of medium polarity and methyl esters of fatty adds. Flash Pyrolysis/GC-MS was applied for investigation of macromolecular organic matter of the samples. Reflected light microscopy was used to find maceral composition and huminite reflectance. All samples organic matter show immature features well corresponding to its values of huminite reflectance (0.17-035%). Rock Eval T-max values were exceptionally low in all cases (on average 387 degrees C) and they show high differentiation according to the lignite lithotypes, with lowest values for xylites. Also other geochemical features of organic matter are lithotype-dependant such as n-alkanes and fatty adds distributions, many biomarkers presence and distribution types and chemical composition of lignite macromolecular fraction. It was possible to asses dominating sources of organic matter using relative concentrations of three groups of compounds with diterpene, hopane and oleanane molecular structures. Most of Miocene detritic lignites come from monocotyledonic material with some of them containing coniferal detritus like needle leaves. Xylitic lignites come from Podocaipaceae, Pinaceae, Cupressaceae, and Taxodiaceae families what is indicated by diterpenoids and sesquitenoids distribution. Detro-xylitic lignites show intermediate geochemical features between detritic and xylitic lignites. (C) 2012 Elsevier B.V. All rights reserved.