The effect of temperature, pressure, maceral composition, and mineral matter on the methane adsorption of coals from the Gething Formation was examined. Data was compared with coals from the Gates Formation in the same area and with coals from Australia. Adsorption capacity in the Gething coals appears to be moderately to strongly affected by the vitrinite (and pseudovitrinite) content and mineral matter which does not only have a diluting effect, but also acts negatively on gas adsorptive capacity. Another explanation for the high gas adsorption capacity in the Gething coals may be related to the presence of free gas, which is more common when coals are below equilibrium moisture in a gas-saturated stratigraphy. Both Gething and Gates coals show an increase in gas-holding capacity, with increasing pressure as a function of vitrinite/inertinite ratio. Such an increase is absent in coals from the Bulli Seam, Sydney Basin, Australia.