We calculate electron-LO-confined and interface-phonon scattering rates in In1-xGaxAs-InP and Hg1-xCdxTe-CdTe quantum wells considering the influence of nonparabolicity on the energy subbands. A simple k . p model is used to take into account this nonparabolicity and a reformulated dielectric continuum slab model is employed to describe the confined phonon modes. We find that the subband nonparabolicity increases the scattering rates significantly for all transitions and that this effect is more pronounced as transitions from higher subbands are involved. We show that this behavior can be understood in terms of the phonon wave vector, the density of final states and the electron-phonon overlap. (C) 1999 American Institute of Physics. [S0021-8979(99)01410-3].851072767281