We have fabricated circular silicon nitride drums of varying diameter (20 μm to 1 mm) and thickness (15 nm-75 nm) using electron beam lithography and measured the dissipation (Q -1) of these amorphous silicon nitride resonators using optical interferometric detection. We observe that the dissipation is strongly dependent on mode type for relatively large, thick membranes as predicted by the current models of dissipation due to clamping loss. However, this dependence is drastically reduced for smaller or thinner resonators, with thinner resonators showing higher quality factors, for low order modes. Highest quality factors that can be reached for these thin resonators seems be limited by an intrinsic mechanism and scales linearly with the diameter of the membrane. Our results are promising for mass sensing and optomechanical applications where low mass and high Qs are desirable. © 2012 American Institute of Physics.