The paper presents a method for the determination of the zone of sensitivity of probes used for the measurement of volumetric moisture in porous media. The probes under analysis were TDR (Time-Domain Reflectometry) probes manufactured at the Institute of Agrophysics, Polish Academy of Sciences, Lublin. Based on the laboratory studies performed it was found that the extent of the sensitivity zone of the field- and laboratory-type probes depends on the water content of the medium in which measurements are conducted. In the case of the laboratory probe (LP/ms), when the measurements are conducted in a completely dry soil, the zone of sensitivity of the probe is the volume of a cuboid with dimensions of 0.6 cm by 5.8 cm and a thickness equal to the diameter of the rods of the LP probe. Whereas, when the soil is saturated with water the zone of sensitivity of the probe is an elliptical cylinder with height of 5.5 cm and radii of 0.5 cm and 0.8 cm. In the case of the field probe (FP/mts), when the measurements are conducted in a completely dry soil, the probe sensitivity zone is an elliptical cylinder with height of 10.2 cm and radii of 0.3 cm and 0.4 cm. Whereas, when the soil is saturated with water that zone is a cylinder with height of 11.2 cm and a circular base with a radius of 1.7 cm.