The effects of phonon confinement on electron–acoustic‐phonon scattering is studied in cylindrical semiconductor quantum wires. In the macroscopic elastic continuum model, the confined‐phonon dispersion relations are obtained for several crystallographic directions with the two cardinal boundary conditions: free‐surface and clamped‐surface boundary conditions. The scattering rates due to the deformation potential interaction are obtained for these confined phonons and are compared with those of bulk‐like phonons for a number of quantum wire materials. The results show that the inclusion of acoustic phonon confinement effects may be crucial for calculating accurate low‐energy electron scattering rates in nanostructures. It is also demonstrated that the scattering rates may be significantly influenced by the direction of phonon propagation, especially for low‐energy electrons. Furthermore, it has been found that there is a scaling rule governing the directional dependence of the scattering rates: the directions characterized by small Poisson ratios exhibit large scattering rates. ©1996 American Institute of Physics.