The effect of suspended solid particles, on the selectivity of a couple of mixing sensitive competitive parallel reactions has been investigated in a stirred tank. Three different solid particles (glass spheres of two sizes and large plastic beads) have been tested. Significant effects on selectivity have been observed at high particle loading, but only with the glass particles. An explanation of the observed behaviour based on the different mechanisms of turbulence modification by the suspended solid has been proposed. Limits and applicability of the chemical method to the investigation of turbulence modulation effects in two-phase systems have also been discussed.