A complex dielectric constant for poplar and monstera delicious's obtained by Ulaby at 10 GHz has been revised at 4 mm band. A measurement setup operating at 4 mm was established for making comparison between modeled and measured values. Results basically show that their electromagnetic transparency increases by drying as expected. While moisture content increases from 0% to 60%, transmitted power decreases from 95% down to 22%; reflection goes up to 50% and the absorption reaches from 1% to 20% for monstera leaf. A model developed for poplar responds much better than the model revised for monstera leaves.