Forced oscillation technique (FOT) has been widely applied to physiological assessment in obstructive lung diseases, and several commercial FOT devises have been available nowadays. However, it is not fully understood whether the impedance values measured with different devices are identical. In the present study, two different kinds of FOT devices, MasterScreen IOS (10S)(CareFusion, San Diego, CA, USA) and MostGraph (MG) (CHEST MJ., Tokyo, Japan) which are currently available in Japan,and also the brand-new and handy device, tremoFlo(TF)(Thorasys, Montreal, Canada) were compared using phantom models. We used phantom models that consist of a flow resister (official standard test load for MG, 2.0 - 9.7 cmH20/1../s), and rigid wooden box as gas compliance (8351). Additionally, we applied ventilation using 1.01 calibration syringe with different rate (0, 10,20, and 30/min). The resistance values varied up to 10% from estimated values in these devices, and there were differences In frequency dependence of the resistance between the devices (Figure). TM showed less frequency dependence than others. The reactance values measured with MG were higher than those of 10S. And IF showed intermediate values between them. The effects of ventilation on the measured impedance values were higher in IOS than MG especially at lower frequencies. TF did not show inconsistent frequency dependency in reactance, but similar dependency in resistance by ventilation. In conclusion, three devices do not always generate the Identical Impedance values, and the differences between these devices should be taken into consideration in the evaluation of clinical data.