In the present work, some static and dynamic properties of trimers containing one benzene molecule and two rare gas atoms are investigated. These trimers can be formed in two different configurations, one in which the two rare gas atoms are placed in opposite sides of the benzene plane, (111), and the other in which the two atoms are placed on the same side, (210). The (111) configuration is more stable than the (210), and both minima are connected by small energy barriers. Accordingly, molecular dynamics simulations show frequent (210) <-> (111) interconversions, even at low temperatures. The time spent in each configuration has been related to the abundance of isomers. It has been found that at temperatures just below the dissociation, when interconversions are quite frequent, the relative abundance of (210) is always higher than that of (111), independently of the nature of the two rare gases.