Various kinds of crystal defects, such as ferroelectric domain boundaries, growth bands, dislocations, subgrain boundaries and cellular structures, etc. in Czochraski-grown ferroelectric LiNbO3 single crystals were investigated by X-ray transmission topographic technique. The defects were identified by means of invisibility conditions using different diffractions, as well as X-ray anomalous scattering effect and optical microscopy. We have discussed the formation of domain boundaries in LiNbO3 and their relation to the growth bands.