The effects of wall diffusing elements on sound-field diffuseness in a tenth-scale model hall were investigated by measuring surface diffusivity of the lateral walls covered with horizontal diffusers. Objective characteristics were investigated using conventional room acoustic parameters and the number of peaks (Np) computed for the measured impulse responses, which were recorded under diffusive and non-diffusive conditions. In addition, as a measure of the perception of diffuse sound fields, the different descriptions for subjective diffuseness were defined in terms of density, decay (early/late) and isotropy of reflections. Results showed that the diffusive surfaces caused a increase in C80, 1-IACCE3 and Np. Auditory experiments revealed that clarity, loudness and intimacy was increased after installing diffusers and the perception of subjective diffuseness was found to be highly correlated with Np.