The electron tomography and transmission electron microscopy studies of the carbides in the 0.5Cr-0.5Mo-0.25V (13HMF) low-alloy steel after service during 160 000 h at 540 °C were carried out. Identification of the carbides was performed by means of electron diffraction analysis. Meso-scale tomography technique, mainly FIB/SEM tomography, was used for detailed characterization of spatial distribution and metrology of the carbides in 13HMF steel. The results achieved confirm the ability of FIB tomography to get 3D reconstruction of internal microstructure of steel as well as to obtain information about the shape and spatial distribution of carbides.