As a part of maintenance of civil engineering structures of Plomin Thermal Power Plant, regular inspection of structures was carried out in order to preserve their structural properties and fulfil the requirements defined by Croatian laws and regulations. Regular inspection of structures included a detailed visual inspection and establishing a preliminary classification of damage (determination of defects essential for maintaining resistance and stability of the structure) of all characteristic elements of bearing and protective structures on which the safety and functionality of the plant depend. Moreover, field and laboratory tests were carried out in order to demonstrate visually assessed categories of concrete and steel damage.