Deliveries of tar, nicotine, CO and CO2 in main stream smoke decreased as the potassium salt content of reconstituted tobacco leaves increased. The peak temperatures of the central region of a burning cone during a puff was in the range 940℃∼430℃ by IR thermal video system. The exogenous Potassium salt contents influenced the reduction of carbon-monoxide delivery through a decrease in the Peak temperature of the burning cone. Consequently, the amount of CO formed in the combustion Process was reduced by potassium salt. Moreover, the temperature of the burning cone was lowered, and the CO formed from carbonaceous reduction was decreased. Key words : carbon monoxide delivery, potassium salt, temperature of burning cone, reconstituted tobacco