A computer model describing the total cigarette pressure drop has been developed by treating the cigarette and its filter as cylinders filled with porous materials. The flow through the filter is laminar, a condition for using the Darcy theory, while the flow through the tobacco rod follows a non-Darcy flow, a laminar / turbulent flow transition. Introducing ventilation in the filter creates gas velocity profile changes and pressure drop gradient changes in the filter and in the tobacco rod that are dependent on the ventilation amount and on the vent location. The analytical solutions are presented for cigarettes with carbon-on-tow / cellulose acetate dual filters. However, the learnings can be applied to the relatively simple CA or paper mono-filters and to the more complex filters such as triple filters or filters containing concentric components. The model can predict the total cigarette pressure drop and the pressure drop of each filter component as one changes the value and/or ventilation position. It can also predict ventilation values if one changes one or both filter components pressure drop values while keeping the tipping paper perforations constant. This general study of the flow dynamics generated the interactive system, called a ventilated filtered cigarette, has resulted in a predictive tool that lends clarity to a very complex system.