Lower or Reduced Ignition Propensity cigarettes (LIP or RIP) is a term used to describe modified cigarettes that demonstrate lowered ignition propensity under specific laboratory tests. These cigarettes must meet standard performance criteria described by the test method established by ASTM E2187-04 regulations in which lit cigarettes must self-extinguish under controlled conditions.Studies have shown that there is a higher correlation between the ASTM performance of cigarettes and the measured diffusivity of CO₂ through the paper than there is with permeability. Therefore cigarette base-paper diffusivity is becoming increasingly important when specifying LIP paper grades.Recently, several studies have sought to identify the base-paper parameters that influence diffusivity and the effects that the latter has on cigarette smoking yields (NFDPM, nicotine and CO). Discussed here are the results of a systematic study which was undertaken in order to investigate the above, across a range of filler and fibre levels and paper permeabilities. The cigarette paper physical characteristics ( e.g. tensile strength, stretch, opacity and whiteness) as a function of the fibre and filler contents of the paper are also discussed. Amongst other findings, the base-paper diffusivity is shown to increase as the filler content is increased and as the fibre content is decreased. In turn, NFDPM and CO yields decrease with increasing diffusivity, as does the puff number. Tensile strengths of the papers are shown to increase as the fibre level is increased and as filler levels and paper permeabilities decrease.