Several boundary conditions have been proposed to stabilize the dimerized structures of finite-length Peierls-Hubbard chains. The effects of different boundary conditions on the lattice structures and the electronic energy spectra have been analysed. It was found that the natural or the fixed-end boundary conditions are more suitable to describe polymer chains with very short lengths than the periodic boundary condition. The competition of electron-electron interactions with electron-phonon interactions in finite-length chains has also been studied.