The main physical parameter of all ventilated filter cigarettes is the filter ventilation. It has been known for many years that these cigarettes have a possibility to achieve major reductions in all noxious smoke components including those in the gas phase, and that filter ventilation is a practical tool for controlling smoke deliveries. The term filter ventilation in this case describes the supply of diluting air to the main-stream smoke via the ventilated cigarette filter. Smoking of a lit cigarette is a nonlinear dynamic process, and filter ventilation depends on the interrelationship between a number of factors. Fortunately, the total ventilation measured on an unlit cigarette during constant and standard air flow at mouth end is somewhat lower than for a lit cigarette. It was shown that linear models used here make it possible to estimate filter ventilation degree for various commercial unlit cigarettes from nondestructive pressure measurements and geometrical data