A tire pressure diagnostic system for vehicles is provided for diagnosing tire pressure for at least one of the tires based on the traveled distance of the vehicle and input indicative of the tire movement. The diagnosis of the tire pressure may be based on comparing the traveled distance of the vehicle with a distance determined based on the output from a tire sensor and a predetermined radius of the tire under proper inflation. The diagnosis of the tire pressure may also be based on comparing an actual radius of the tire, determined by the traveled distance of the vehicle, with a predetermined radius of the tire under proper inflation. The diagnosis of the tire pressure may further be based on comparing the number of wheel rotations, determined from the tire movement input, with a number of rotations determined based on the traveled distance and the predetermined radius of the tire under proper inflation.