A density functional perturbation theory, which is based on the modified fundamental-measure theory to the hard-sphere repulsion and the first-order mean-filed approximation to the long-range attractive or repulsive contributions, has been proposed in order to study the structural properties of hard-core Yukawa (HCY) fluids. The advantage of the present theory is the simplicity of the calculation of the long-range attractive or repulsive interaction. The calculation shows that the present theory excellently describes the density behaviors of the attractive and repulsive HCY fluids near a planar slit pore. However, at low temperature the accuracy for the attractive HCY fluids slightly deteriorates when increasing the bulk density. The test particle method has been applied to calculate the radial distribution function of the uniform HCY fluids. The present theory predicts an accurate radial distribution function of the attractive and repulsive HCY fluid even for the high density. The phase behaviors of an attractive HCY fluid restricted to the nanosized slit pores have been studied at the subcritical temperature. The results show that the vapor is the stable phase at the narrow slit pores and the liquid is the stable phase at the wide slit pores. The wide liquid-vapor coexistence curve, which implies the wide range of metastable liquid-vapor states. is observed at wide slit pores. The increase of slit width leads to a shift of the liquid-vapor coexistence curve towards lower value of chemical potential. (C) 2011 Elsevier B.V. All rights reserved.