The grand canonical Monte Carlo (GCMC) simulation method is used to study adsorption of methane in finite carbon slits. Simple Lennard-Jones potential is used to describe intermolecular interactions for methane. Slits between two identical carbon cylinders and between a cylinder and a planar infinite solid surface are considered. Adsorption field non-uniformity generated by edges leads to shifts of adsorption isotherms and to changes of the fluid local structure in pores. The enhancement of edge effects at larger distances from the wall is demonstrated. The behavior of the fluid density in finite slits predicted from the asymptotic theory has been confirmed.