Changes in the internal structure of the trunk of standing trees for example. Decay and emptiness are often not possible to identify visually. Computed tomography offers very good support in the diagnostic assessment of the health of trees. Recently, there are innovative testing methods, which include: electrical tomography, computed tomography, and acoustic mapping root systems of trees using the GPR system. Precision measuring instruments used in these methods, especially due to its non-invasive nature, suited perfectly in practice. The results of diagnosis are presented on a regular basis, which makes already in the field, we can make a preliminary assessment of the state of health of the tree.