Superlattice structures fabricated using high (2.8 eV) and low (1.5 eV) band gap modulated diamond-like carbon (DLC) thin film layers give evidence of quantum size effects. The DLC films were deposited using a CH4-Ar gas mixture in a 13.56 MHz r.f. powered plasma enhanced chemical vapour deposition (PECVD) system under computer control. Glancing angle X-ray diffraction was used to verify the existence of superlattice potential barriers. X-ray photoelectron spectroscopy data coupled with electronic conduction analysis was used to construct an electronic band diagram for the amorphous DLC superlattice structure. The ’blue shift’ observed in the optical band gap was examined. Analysis of the increase in optical band gap with decreasing well width gives an effective mass of 0.067m(0) for the electrons and holes (which are assumed to be equal).