In this paper, a statistical analysis of cement composites with wood biomass ash was made to define the relationship between certain parameters and properties. The paper consists of a theoretical and an experimental part. The theoretical part describes wood biomass power plants, their mode of operation, types of fuel, current quantity, and plans regarding renewable energy sources. Wood biomass ash, its origin, amount, chemical composition, and further use are also described. In the experimental part, the correlation coefficient is explained as a method used during the statistical processing of the results. For five different mixes, the following properties were determined: properties in the fresh state (density, temperature, pore content, and consistency), mechanical properties (tensile and compressive strength), and deformations (shrinkage due to drying and autogenous deformation). Correlation coefficients were calculated for the following parameters: the dependence of the tested properties on the content of wood biomass ash, the influence of properties in the fresh state on mechanical characteristics and deformations, and the connection of mechanical properties with deformations. Based on the calculated correlation coefficients, a conclusion was made about the influence of wood biomass ash on the characteristics of cement mortar.