<p>Composting is used as a method of recycling spent coffee grounds (SCG). Chemical analysis revealed that coffee grounds compost (CGC) has a lower content of crude fat, and higher contents of crude protein and ash, than those of SCG. Activated carbons were prepared from CGC and SCG, and their chemical compositions and pore structures were compared. The N/C ratios of activated CGC (CGCAC) and activated SGC (SCGAC) were 2.1 and 1.9 wt%, respectively, being similar, although the raw CGC originally had a N/C ratio twice (10 wt%) that of the raw SCG (4.5 wt%). The BJH method with nitrogen adsorption revealed that CGCAC had a larger mesopore diameter (10.6 nm) than SCGAC (4.8 nm), while the micropore diameters were almost the same (about 0.4 nm). It is suggested that changing the ratio of the components by composting, especially ash as the activation catalyst, affects the mesopore structure of the activated carbon.</p>