The article deals with correlation analysis of district heating processes using correlation matrixes and correlation scatter plots. The district heating (DH) processes are described by 6 thermal-energetic parameters and 7 hydraulic parameters as, for instance, supply and return water temperature, Ts and Tr, outdoor temperature, Tout, supply water flux, V, and so on. Several correlation matrixes have been computed on the basis of different DH-parameter data sets obtained in different time periods, e.g., October&April or Januar&Februar months. It has been stated that correlation matrixes are sensitive instrument for estimation of so called regressor-regresent pairs of DH-parameters that one can use for corresponding regression models as well as for digital modeling and control of a DH system. The correlation scatter plots of the estimated regressor-regresent pairs are used in order to explore quickly eventual regression model functional form by corresponding graphs.