The effect of cement fineness on the fresh state and rheological properties as well as compressive strength of cementitious systems was investigated. A CEM I 42.5R portland cement containing 7.92% C 3A and sulfate resisting cement containing 3.58% C 3A were used. The cements were ground to 4 different Blaine finenesses, ranging from 2800 to 4500 cm 2/g. In the absence of water-reducing admixture, the water requirement of mixtures increased with an increase in the cement fineness. Thus, the fresh state properties of the mixtures were affected negatively. However, surprisingly, a reverse behavior was observed in the mixtures containing water-reducing admixtures, that is, an increase of the cement fineness increased the effectiveness of the admixture; consequently, the fresh state properties of the mixtures were improved. This seems to have been caused from the higher adsorption of the admixture on finer cement grains than on the coarser particles. Moreover, as expected, the strength of the mortar and concrete mixtures increased along with the increase in cement fineness and its C3A content.