We present the results of Monte Carlo simulations of chains confined in a very narrow slit, in the limit of strongly attractive walls. Simulations are performed in the canonical ensemble, and the chain increment method of Kumar et al. (Phys. Rec, Lett., 66, 2935, 1991) is applied to obtain the chemical potentials of the polymers in the pore and the bulk. Results are summarized in three groups : conformation of chains inside the pore, chemical potentials of confined polymers and adsorption isotherms. Due to the proximity between the walls and the strong attraction they exert on the polymers, a strong bridging effect is observed. The incremental chemical potential of a chain in the pore becomes independent of chain length for long chains, as seen previously for chains in the bulk. The influence of the pore width on the adsorption behavior is also discussed.