In the present work, radon adsorption by common silhouette plants often used in Iraq for decoration was tested. Two similar groups of silhouette plants were analyzed (twelve pairs of popular indoor plant species). The first was the control group, the second the exposed group. The plants were placed in a semi-closed plastic box with radium point sources have 348.5 kBq activity (uncertainty = 5% at k = 2) as sources of artificial radon gas. The specific activity of the plant leaves was measured with a NaI (Tl) gamma spectroscopy detector. Radon adsorption rate in each species was obtained by adopted a new mathematical relation from the variation of Bi-214 specific activity measured in the leaves of the two plant groups. Plants showed different capability to adsorbed radon from the environment according to their shape and microscopic composition. The present results show that the highest adsorption radon rate calculated in the studied plants is (35.1%), it's detected in dieffenbachia which has oval leaves with a large surface area, thick veins visually, and big holes when examined under optical microscope, while the lowest rate which is (10.1%) was detected in ivy (Potise) that has a small heart-shaped leaves visually with small and compact holes microscopically. In general, indoor plants can adsorb radon gas and purify indoor air with different capability.