We have studied the lateral waveguiding properties of gain‐guided and index‐guided II–VI lasers under pulsed conditions and their influence on threshold current densityJthand differential quantum efficiency &eegr;. Thermal index guiding was found to reduce the astigmatism of the gain‐guided devices. The thermally induced lateral field confinement leads to a lowering ofJthand an increase of &eegr; with pulse width with a maximum after a few &mgr;s because of maximum overlap of the near field with the gain profile. For the index‐guided devices the lateral waveguiding is fully determined by the built‐in refractive index profile and no dependencies on pulse width are observed. ©1996 American Institute of Physics.