  We study the second harmonic generation (SHG) in a suspension of small
spherical particles confined within a slab, assuming undepleted pump and
applying (i) single scattering approximation and (ii) diffusion approximation.
In the case (i), the angular diagram, the differential and total crossections
of the SHG process, as well as the average cosine of SH scattering angle are
calculated. In the case (ii), the average SH intensity is found to show no
explicit dependence on the linear scattering properties of the suspension. The
average intensity of SH wave scales as I_0 L / \Lambda_2 in both cases (i) and
(ii), where I_0 is the intensity of the incident wave, L is the slab thickness,
and \Lambda_2 is an intensity-dependent "SH scattering" length.
