The distribution of phenyldibenzofurans (PhDBFs) and methyldibenzofurans (MDBFs) and their potential implications in petroleum organic geochemistry have been investigated for sediment extracts and crude oils derived from lacustrine shale, marine shale, marine carbonate, and terrestrial (fluvial/deltaic/fresh water) mudstone. PhDBF isomers in a set of lacustrine shales from the Liaohe Basin (East China) are identified in the m/z 244 mass chromatograms of the aromatic fraction by coinjection of internal synthetic standards on a high resolution capillary column (HP-SMS). The results show that the relative abundance of 4-PhDBF/2-PhDBF and 4-PhDBF/(2-PhDBF+3-PhDBF) increase gradually with increasing burial depth and maturity (R-0 >= 0.6%), and have a good correlation with vitrinite reflectance in lacustrine shales from wells 5202 and SG1 in the Liaohe Basin. These two ratios, defined as phenyldibenzofuran ratio-1 and-2 (PhFR-1 and PhFR-2), may be potential maturity indicators for mature sediments in this study. Four MDBF isomers are also ubiquitously present in all samples studied, and show regular distribution patterns in the m/z 182 mass chromatograms of the aromatic fraction. In rocks and oils derived from the terrestrial depositional environments of the Liaohe and Beibuwan Basins (China), there is a marked predominance of 2- and 3-MDBF over 4- and 1-MDBF, and three peaks formed by 4-, 2-+3-, and 1-MDBF show a reversed "V-shaped" distribution pattern in the m/z 244 mass chromatograms. However, for samples derived from the marine environment in the Termit (Africa) and Tarim (China) Basins, the abundances of 4-MDBF generally exceed or approach those of 2- and 3-MDBF. A cross-plot of (1+4)-/(2+3)-MDBF versus Pr/Ph ratios measured on rocks and oils from various depositional environments is used here to investigate the effect of the depositional environment and lithology on the distribution patterns of four MDBF isomers. This cross-plot classified the samples in this study into the following five environmental/lithological zones: marine carbonate; marine carbonate and shale; marine shale; lacustrine shale; and fluvial/deltaic/fresh water lacustrine shales. Samples from various depositional environments in this study can be basically distinguished.