A quantitative model describing the effects of puffing conditions on the level of filter ventilation was developed and evaluated. The development of the model was based on a quadratic flow-pressure drop relationship which was validated with experimental measurements for numerous plug wraps, tipping papers, and combinations of the two. This relationship was used to derive an equation describing the level of filter ventilation as a function of the flow rate of air exiting the filter. This equation was shown to accurately predict the measured ventilations of six brands of commercial cigarettes over a range of continuous flow rates. The instantaneous ventilation values predicted by the equation were utilized to model ventilation during a puff by integrating the equation with respect to flow rate over the duration of the puff. This method for predicting the effects of specific puffing conditions on ventilation was demonstrated for sinusoidally shaped puffs spanning a wide range of volume and duration. Finally, the effects on the flow dependence of ventilation of different combinations of plug wrap and tipping papers were described qualitatively based on experimental measurements of paper flow-pressure drop linearity.