In this work, mass spectrometry and optical emission spectroscopy techniques were used to monitor the molecular and atomic neutral species during SF 6 /CF 4 , SF 6 /O 2 and CF 4 /O 2 plasmas generated in a radio-frequency Hollow Cathode Reactive Ion Etching (HCRIE) reactor keeping constant the following operational conditions: total gas flow rate, gas pressure, and discharge power. The investigations were aimed to understand the chemistry behavior of plasmas generated with SF 6 and CF 4 mixtures or mixed separately with O 2 . The neutral mass spectrometry analysis showed a high concentration of gas species namely SF 5 + (parent specie = SF 6 ), SF 3 + (SF 4 ), CF 3 + (CF 4 ) and HF + (HF) in SF 6 /CF 4 plasmas, SF 5 + , SF 3 + , O 2 + (O 2 ), F + (F) and HF + in SF 6 /O 2 plasmas and CF 3 + , O 2 + , CO 2 + (CO 2 ) and HF + in CF 4 /O 2 plasmas. The presence of other species was observed in quantities lower than 1% of total gas pressure. It was used the actinometry method to monitor the atomic fluorine (F) concentration during discharge operation. Higher density of F was observed in all experiments, varying from (2.8–9.5) × 10 19 m −3 in SF 6 /CF 4 plasmas, (0.2–1.7) × 10 20 m −3 in SF 6 /O 2 plasmas and (0.06–1.17) × 10 20 m −3 in CF 4 /O 2 plasmas. The addition of CF 4 in SF 6 plasma reduces monotonically the F concentration when compared with the SF 6 /O 2 and CF 4 /O 2 plasmas that promotes an increase of F for low O 2 concentrations. This effect shows the importance of oxygen species in the dissociative processes of the fluorine-based plasma also for this type of plasma reactor. Moreover, it is highlighted the higher concentrations of HF in gas phase that promotes reactions paths that decrease the F species in gas/plasma phase.