In this study, limestone samples were investigated in terms of grinding product particle size distribution (PSD) differentiations after microwave treatment. Initially, collected limestone samples (a total of 58 sample) were crushed and prepared for microwave treatment. In order to observe the effect of microwave treatment, 58 of these samples were ground directly while the other 58 samples were objected to microwave treatment (5 min, 180 W) prior to the grinding. In this paper, size parameters (D-10, D-50, D-90, D-32, and D-43) and their corresponding differentiations after microwave treatment were evaluated. As regards to the finding of this study, microwave treatment prior to grinding can be claimed to ease the grinding, and finer size distribution can be obtained especially for lower Fe2O3 content samples. It was also found out the fact that MgO and CaO content of samples have influenced the abovementioned PSD differentiation to some extent.