This paper presents an overview of laboratory testing carried out to determine the influence of fly ash, as a component in cement mixture, on physical-mechanical properties of cement. Fly ash, used in this testing, was treated by different physical methods – grinding, very fine grinding and classification. The addition of fly ash varied from 10 to 50% by weight in the mixtures with cement. In the first instance, the results were evaluated by the most important criteria, the compressive strenght of mortar containing prepared mixtures. In addition to that, the flexural strength of mortar, soundness of cement pastes, initial and final setting time, as well as the amount of water, required to produce the standard consistency of cement paste, were also investigated. The reported values have completly satisfied the appropriate standard.