In previous experiments, using a, RF plasma generator at low power, we have grown diamond like carbon films (DLC), using a hydrocarbon plasma, without the use of a catalyzer precursor[1]. In order to better understand the relationship between the properties of the resulting DLC films and the RF plasma parameters, we have performed detailed optical emission spectroscopy (OES) observations of RF hydrocarbon plasmas, under identical conditions to those used for DLC films growth. The experiments were performed in a low power capacitively coupled RE (13.6 MHz) plasma generator, operating at 30 W. Working gases were acetylene and hydrogen. The optical emission of the RF plasma was recorded, under different operational conditions, with a spectrometer, and an f-f light collection arrangement was used to achieve spatial resolution. The relative emission of the different molecular species was found to depend on the C2H2:H-2 flow ratio. Based on the OES observations, we present a description of plasma conditions in a low power RF hydrocarbon plasma reactor.