The critical properties of the Lennard-Jones fluid in slitlike pores of different widths have been studiedby the Gibbs ensemble Monte Carlo method and the lattice gas model. Graphite pores up to 10 moleculardiameters in width and similar pores with weaker solid−fluid interactions have been considered. Stronglayering of the adsorbate in the graphite pores confirmed the applicability of the lattice gas model to suchsystems. The vapor−liquid phase diagrams for the confined fluids obtained with the two methods are inreasonable agreement with each other. Linear dependence of the critical temperature on the inverse porewidth was found. It is demonstrated that the critical temperature may depend strongly on the strengthof the sold−fluid interactions. The lattice gas model showed nonmonotonic dependence of the criticaldensity on the pore width.