Pulsed radiation propagating through a layer of a scattering medium undergoes distortions caused by multiple scattering. The results of numerical calculations of pulse waveforms for media with different scattering phase functions are presented. It is demonstrated that the scattered radiation waveform is not described by diffusion theories even for sufficiently large optical thicknesses (tau approximately 10-20) but is described, as a rule, by a bimodal distribution. Only when the optical thickness significantly increases (tau>100-150), the photon distribution over the free paths acquires the unimodal diffusion form.