An aging study of fresh deposits from a laboratory-scale bitumen coker was conducted at the temperature of 550 C to examine the evolution of deposit composition and structure over time and to rationalize the differences between the laboratory deposits and industrial samples. Although the fresh laboratory deposits are much different from the industrial deposits, after days to weeks of aging at elevated temperature, the H/C ratio, thermal behavior, C-13 solid-state nuclear magnetic resonance (C-13 NMR), and diffuse- reflectance infrared Fourier (DRIFT) spectra of the laboratory deposits become very similar to those of the graphitic industrial deposits. The differences in morphology which remain after aging are attributed to the difference in hydrodynamic conditions during the deposit laydown. The various techniques studied yielded a consistent picture of the evolution from the heavy fluid phase components which initially deposit from the vapor to the massive graphitic deposit found in the industrial coker cyclone exit tube.