Coal-derived hydrocarbons from Middle-Lower Jurassic coal-bearing strata in northwestern China are distributed in the Tarim, Junggar, Qaidam, and Turpan-Harmi basins. The former three basins are dominated by coal-derived gas fields, distributed in Cretaceous and Tertiary strata. Turpan-Harmi basin is characterized by coal-derived oil fields which occur in the coal measures. Based on analysis of gas components and carbon isotopic compositions from these basins, three conclusions are drawn in this contribution: 1) Alkane gases with reservoirs of coal measures have no carbon isotopic reversal, whereas alkane gases with reservoirs not of coal measures the extent of carbon isotopic reversal increases with increasing maturity; 2) Coal-derived alkane gases with high delta(13)C values are found in the Tarim and Qaidam basins (delta(13)C(1): -19.0 to -29.9 parts per thousand; delta(13)C(2): -18.8 to -27.1 parts per thousand), and those with lowest delta(13)C values occur in the Turpan-Harmi and Junggar basins (delta(13)C(1): -40.1 to -44.0 parts per thousand; delta(13)C(2): -24.7 to -27.9 parts per thousand); and 3) Individual specific carbon isotopic compositions of light hydrocarbons (C(5-8)) in the coal-derived gases are lower than those in the oil-associated gases. The discovered carbon isotopic reversal of coal-derived gases is caused by isotopic fractionation during migration and secondary alteration. The high and low carbon isotopic values of coal-derived gases in China may have some significance on global natural gas research, especially the low carbon isotope value of methane may provide some information for early thermogenic gases. Coal-derived methane typically has much heavier delta(13)C than that of oil-associated methane, and this can be used for gas-source rock correlation. The heavy carbon isotope of coal-derived ethane is a common phenomenon in China and it shed lights on the discrimination of gas origin. Since most giant gas fields are of coal-derived origin, comparative studies on coal-derived and oil-associated gases have great significance on future natural gas exploration in the world. (C) 2009 Elsevier B.V. All rights reserved.