The critical properties of the Lennard-Jones fluid in slitlike pores of different widths have been studied by the Gibbs ensemble Monte Carlo method and the lattice gas model. Graphite pores up to 10 molecular diameters in width and similar pores with weaker solid-fluid interactions have been considered. Strong layering of the adsorbate in the graphite pores confirmed the applicability of the lattice gas model to such systems. The vapor-liquid phase diagrams for the confined fluids obtained with the two methods are in reasonable agreement with each other. Linear dependence of the critical temperature on the inverse pore width was found. It is demonstrated that the critical temperature may depend strongly on the strength of the sold-fluid interactions. The lattice gas model showed nonmonotonic dependence of the critical density on the pore width.