Coal samples from Florina (Vevi), Lava, Moschopotamos and Kalavryta basins, Greece, have been subjected to petrographic and organic geochemical analysis. The reflectance of the samples ranged from 0.26% to 0.42%, which ranks them as soft brown coals and sub-bituminous C coals. Lower reflectance values were encountered in the Florina and Kalavryta coals, whereas higher values were obtained for Lava and Moschopotamos samples. Maceral composition of the samples from the Florina area shows a high concentration of textinite A and texto-ulminite A. The samples from the Lava and Moschopotamos area are comparatively rich in humodetrinite. Samples from Florina are rich in resinite, whereas samples from Lava are rich in liptodetrinite. Rock–Eval pyrolysis data show that the samples from Florina and Kalavryta have generally high HI, SI and S2 and low T max values. The coal samples from Moschopotamos and Lava show the opposite, having low HI, S1 and S2 values. These distinct differences are related to the maceral composition (tissue rich in resinitic material) and rank of the coals. Gas chromatography of the saturate fraction indicates that the samples from the Lava and Moschopotamos are rich in n-alkanes from n-C 23 to n-C 33. In contrast, the samples from Florina are rich in diterpanes, whereas those from Kalavryta are rich in sesquiterpenoids. Gas-chromatography-mass spectrometry of the saturate fraction reveals that the diterpenoids present in the lignites from Kalavryta are derivatives of abietanic acid and pimaric acid, which are found in Pinaceae. The lignites from Florina mainly contain the diterpane, phyllocladane, which implies an input from Cupressaceae and/or Taxodiacaea. The difference in the composition of these xylitic lignites may be attributed to differences in gymnosperm input as a response to climatic change, as the Kalavryta coals are of Pliocene age, whereas the Florina coals are of Miocene age. The study suggests that the petrology and organic geochemistry of these coals are related to the different peat-forming plant communities that were present in the Florina, Kalavryta, Lava and Moschopotamos basins. A mainly non-woody, angiosperm-dominated vegetation made up the peat that went to form the coal deposits of Lava and Moschopotamos, while the Florina and Kalavryta lignites were formed by peats derived mainly from gymnosperms.