Piezoelectric coefficients gij represent a link between an external mechanical stress applied to a sample and an electric field formed by polarisation charges of the sample as a result of the direct piezoelectric effect. The piezoelectric coefficients gij also characterise a link between a strain and electric displacement at the converse piezoelectric effect. The piezoelectric sensitivity associated with gij is of importance for sensor, energy-harvesting, acoustic, and hydroacoustic applications, for piezo-ignition systems, etc. Examples of the effective piezoelectric coefficients max and their links to the piezoelectric coefficients are discussed for piezo-active composites with various connectivity patterns (2–2-type, 1–3-type, 1–1-type, 0–3-type, and 3–β composites). The important role of the microgeometric factor and polymer component at achieving the large values of of the composite is shown.