This paper deals with the investigation of structural parameters of different cokes: petroleum coke, pitch coke, pure metallurgical coke, and metallurgical coke produced from coal with the addition of atmospheric residue and coal tar pitch. Crystallographic parameters (crystallite height, L-c and interlayer spacing, d(002)) were measured by X-ray diffraction after heat treatment at 1200, 1600, 2000 and 2400 degrees C (heating rate 10 degrees C/min, heating time 4 h). Surface morphology was determined by means of scanning electron microscopy (SEM analysis) at 1200 and 2400 degrees C. The results show that temperature and the type of coke have an important effect on these structural parameters. Maximum L-c values and lowest d(002) values were obtained for the pitch coke and the coke produced from coal with 20 wt.% coal tar pitch addition heated at 2400 degrees C. Differences in crystallographic parameters of the cokes examined also become manifest through their surface morphology. After heat treatment at 2400 degrees C, the pitch coke and the coke produced with addition of coal tar pitch brought about the development of more lamellar structural components.